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The purpose of this thread is to help focus the attention of the community on posts that may require reopen and undeletion votes. A request should be posted as an answer below (one request per answer).

Some guidelines:

  • Please be polite, and respect the many different viewpoints in our diverse community. This goes for the person making the request as well as those commenting on it.

  • There is a reopen queue. Please wait until a post has gone through this queue, before posting here. Notice that the first edit after the question was put on-hold pushes the question into reopen review queue, if the edit was done within 5 days of closure. So does a reopen vote. (If the review has already been finished, it is shown on the timeline of the question.) In doubt, wait 24 hours after the last substantive action.

  • To inform readers of the current (and past) states of the targeted post, please add once the request resulted in some action the information Reopened or Undeleted at the start. (If it the action is undone, add this too, like Reopened, reclosed.)

  • Do not only post a request, like "request reopening of ". Instead make a case for your concern. Yet keep in mind that it can be easier to get your request handled if you try to frame in a away that takes the feedback the post received into account in a positive way rather then seeking confrontation. Also, try to improve the post before posting here.

  • In case of "small" requests, like one missing vote, it can make sense to ask in chat instead of posting here. The room CRUDE is a reasonable place for such requests. The same guidelines apply there.


Earlier versions of this thread that served as a model:

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109 Answers 109

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Deleted by a moderator

This question was closed and deleted with the reason given "This question is missing context or other detail". However the author of the question explained both his educational background (he is an undergraduate) and his motivation for the question (it was information that wasn't covered in his degree).

This information is sufficient context to give an answer, indeed I can't think of any further context that a person asking the question could add that would result in a better answer.

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    $\begingroup$ The body does not even contain the question. That question-post is poor, and the thread of very limited value overall. The answers being pretty terse and not giving enough detail. // Added: Given the comment below I'll add that it was not I that deleted it. $\endgroup$ – quid May 9 at 6:59
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    $\begingroup$ As far as I can tell, if a post was deleted by a moderator - like in this case - the deletion cannot be reversed by regular users. (Of course, voting your posts still can show to which extent users support undeletion - and if there is some support, perhaps moderators might have a look at the the question again.) $\endgroup$ – Martin Sleziak May 9 at 6:59
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    $\begingroup$ @quid can you explain what is poor about the question? Broadly speaking pen and paper methods of factoring numbers is a subject that the site should have coverage of. $\endgroup$ – Q the Platypus May 9 at 23:32
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    $\begingroup$ I already mentioned one shortcoming. Further and more drastically, the question does not contain any relevant thought of the OP or even just explanation what they want that information for. For example, do they realize that one can easily recognize that some number are not prime? How would they approach the problem for two digit numbers? Or something else, would all make the question better. That said, the question would arguably be saveable. But what for? The answers are low quality. I'd prefer somebody, say my students, won't find any information here rather than those answers. $\endgroup$ – quid May 10 at 9:55
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    $\begingroup$ Fortunately similar information is available in other and better threads. In my opinion, the site is quite simply better without this thread. $\endgroup$ – quid May 10 at 9:57
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Reopened, closed again as duplicate

I nominate reopening Non-negative integer solution for $ax + by = c$. The OP updated the question with what I consider to be sufficient context after the first close vote, but before the final one. As I thought the updated text then made it an appropriate question, I provided an answer. After I discovered it was closed, I flagged it for reopening, but this was declined. FYI, the full timeline is here. Please check this question to see if it should be reopened. Thanks.

Update: As explained in the comments, the question is really a duplicate. It's now closed again for what I consider an appropriate reason, i.e., as a duplicate.

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    $\begingroup$ It's a duplicate of math.stackexchange.com/questions/490602/… and probably several others. If it's reopened, it should immediately be closed as a duplicate. $\endgroup$ – Gerry Myerson May 28 at 6:37
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    $\begingroup$ @GerryMyerson I appreciate your feedback. Since it's a duplicate, I don't have any problem with closing it as such (if it's first reopened), and will even vote to do so. $\endgroup$ – John Omielan May 28 at 6:44
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    $\begingroup$ @GerryMyerson I just gave the last vote to reopen the question. To follow through on what I stated above, I then tried to vote to close as a duplicate. However, because I gave a vote to close on April 18 and then retracted it (due to the OP giving more context so I thought it shouldn't close), the system won't let me vote to close it again, even though it's gone through a close/reopen cycle. As such, perhaps you may wish to start the process of closing it now as a duplicate. Thanks. $\endgroup$ – John Omielan Jun 1 at 3:09
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Closed, deleted, undeleted, deleted, undeleted, deleted, undeleted, deleted, undeleted, reopened.

Unfortunately, the question I asked Why is the zero polynomial the only one to have infinite roots? was put on hold as off-topic first, then closed, and then deleted. I edited it much for it to be reopened, but it wasn't reopened. I apologise if it was off- topic to you, but I edited it. If it being off topic yet, kindly suggest improvement or undelete it please.


Note (quid): I reopened this now. The mass-editing and double posting OP is gone, the question is simple and a bit confused, but arguably not overly contrived and understandable, and answered. It's not impossible somebody else might find this useful at some point. Let's move on.

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    $\begingroup$ Have you finally made up your mind between "Wikipedia" and "wikipedia"? $\endgroup$ – Did Feb 3 at 21:37
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Undeleted

Please consider undeleting the question:

Intersection of Normal closure and Center

The OP deleted question after answer was given.

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    $\begingroup$ I undeleted, but maybe write a proper answer next time. $\endgroup$ – quid Jun 4 at 13:39
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    $\begingroup$ @quid I like hints (plus its a pretty straightforward question - I spent a while debating whether to just leave it at "kill $t$"). $\endgroup$ – user1729 Jun 4 at 13:43
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    $\begingroup$ Then maybe start a Q&H site. This is Q&A site. $\endgroup$ – quid Jun 4 at 18:09
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    $\begingroup$ @quid the hint was clearly sufficient for the OP - they wouldn't have deleted their question otherwise! :-) $\endgroup$ – user1729 Jun 4 at 19:00
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    $\begingroup$ That's pretty irrelevant to my point. Further, If "sufficient for the OP" is your main concern, why do you bother us with an undelete request? // The way that hint was orginally presented to me personally made it pretty confusing. The new format is in a way better. But, frankly I just despise that form. I know it's popular but I think it's terrible style. $\endgroup$ – quid Jun 4 at 22:55
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Undeleted, deleted, undeleted, reopened, put on hold, deleted, undeleted again (the war goes on)

Undelete please this topic: Minimum of $x^2+y^2$ for $\frac1x+\frac8y=1$

The topic starter solved this problem by using "differentiation or Lagrange multipliers", but he looked for a short solution and he got it.

Thank you!

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Undeleted, Reopened

Please consider undeleting and reopening this post: Convergence or diverge of the series $\sum_{n=1}^\infty\left(\frac{1}{n} - e^{-n^2}\right)$

OP clearly indicated his/her thoughts at the beginning of the post, and there is a well written (with 10 upvotes) answer.

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Please consider undeleting this well-received (31 net upvotes) question under the tag of probability: Probability of drawing the Jack of Hearts?

There are useful discussion and several good answers, one of which has 74 upvotes.

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Undeleted, reopened

Please consider undeleting the post:

Reference Request: Proof of H. Steinhaus' Lattice-Point Theorem, created on Mar 11 '17.

This question has two good answers.

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    $\begingroup$ Why don't you people leave these old questions alone? They're really not doing anyone any harm by being left on the site. $\endgroup$ – Gerry Myerson Jul 2 at 3:23
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    $\begingroup$ @GerryMyerson "They're really not doing anyone any harm by being left on the site. " Got debunked numerous times. It's almost hard to believe that you just keep repeating it. To reiterate, not only does precedent get invoked in discussion, users also tend to go by the question they see when deciding how to ask. Of course one can consider this as not enough reason to delete them, but to simply claim "not doing anyone any harm" is just false. $\endgroup$ – quid Jul 9 at 13:48
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    $\begingroup$ On the post generally, at least one might have restored the earlier more complete version. The current version is completely unclear as question, there is arguably more than one result that could be meant. $\endgroup$ – quid Jul 9 at 13:55
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    $\begingroup$ And one more thing @GerryMyerson to refer to a question from 2017 under "these old questions" is rather odd. Discussions about quality of questions were well advanced by then. $\endgroup$ – quid Jul 9 at 14:00
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    $\begingroup$ OK, @quid, I've rolled back to a more complete version. $\endgroup$ – Gerry Myerson Jul 10 at 0:17
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Undeleted, then closed and deleted

I think there's a consensus that we undelete questions when they are deleted by the user who posted them after someone else has posted an answer (see, for example, the comment here: https://math.stackexchange.com/questions/2759560/extending-the-triangle-inequality#comment5694741_2759560). In accordance with that consensus, I propose undeletion of https://math.stackexchange.com/questions/2840649/solutions-to-sum-j-ok-r-j23r-j2-equiv-0-mod-p

Now I'll own up that I'm the one who posted the answer to the question. My answer was exceedingly terse, and came out of a review with the note, "This does not provide an answer to the question (and so on, and so forth)." But it does provide an answer. The question was to prove or disprove that there are no solutions to a certain equation (congruence, actually, but never mind), and my answer gave a solution.

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    $\begingroup$ Is this actually a consensus? $\endgroup$ – Did Jul 23 '18 at 12:30
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    $\begingroup$ @Did, if you look at the previous edition of this thread, you'll find that in April-May, GNU Supporter posted 4 requests for undeletion, all on the grounds that OP had deleted a question after receiving an answer, and all four questions were undeleted. $\endgroup$ – Gerry Myerson Jul 23 '18 at 12:51
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    $\begingroup$ Yes, and? $ $ $ $ $\endgroup$ – Did Jul 23 '18 at 18:11
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    $\begingroup$ @Did For what it's worth, I have the same impression about the consensus. Preventing an asker from covering up their own question seems to be something the community values, even if it's closed later. $\endgroup$ – user296602 Jul 23 '18 at 18:35
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    $\begingroup$ @T.Bongers (and also Gerry Myerson): I think that there is a moderate consensus that it is bad form to ask a question, get an answer, then delete the question. It belies an ignorance of the functioning of the site (i.e. questions are supposed to be helpful to everyone, not just the one person asking the question). However, in this particular case, the question is of pretty low quality, and should be closed and deleted (in my opinion). It seems like a waste of resources to have opened it back up again... $\endgroup$ – Xander Henderson Jul 23 '18 at 19:00
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    $\begingroup$ For what it's worth, I have expanded my answer to the question on main. $\endgroup$ – Gerry Myerson Jul 24 '18 at 0:34
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    $\begingroup$ "For what it's worth, I have expanded my answer to the question on main." On this topic, my understanding is that the consensus is that a good (or even great) answer is not really enough to justify keeping a poor question around. This and this are relevant. $\endgroup$ – Xander Henderson Jul 24 '18 at 13:27
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    $\begingroup$ @Xander, the highest-voted answers and comments on your first link hardly support your understanding. The second link, even there there is considerable support for not deleting questions with good answers. I'm not convinced there is, was, or ever will be a consensus on this issue. A majority, maybe, but no consensus. $\endgroup$ – Gerry Myerson Jul 24 '18 at 21:31
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    $\begingroup$ @GerryMyerson I think you and I must be reading very different answers. In answer to the question of whether bad questions with good answers should be preserved, my reading of the top three answers ((1), (2), (3)) suggest that it might be worth protecting a poor question if it hosts an excellent answer. $\endgroup$ – Xander Henderson Jul 24 '18 at 22:54
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    $\begingroup$ On the question of upvoting poor questions with good answers, the top voted answer is this one, essentially "I don't do it, but there could be an argument in favor of it." The second answer is similar, with the idea being that a good answer should be preserved if it might be helpful for others in the future. $\endgroup$ – Xander Henderson Jul 24 '18 at 22:55
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    $\begingroup$ In both cases, it seems clear to me that the consensus is that it might be reasonable to preserve a poor question if it attracted a really good, useful, generally helpful answer. Again, a good answer (or possibly even a great answer) is not, by itself, enough to preserve a poor question. $\endgroup$ – Xander Henderson Jul 24 '18 at 22:58
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    $\begingroup$ Finally, I note that I made my initial comment in response to your assertion that you have improved your answer. Are you further asserting that the improvements created something that is of such lasting value that it will be beneficial beyond asking that poor question? Despite the fact that this question and answer have been the topic of discussion here for a couple of days, your answer has not attracted any upvotes... $\endgroup$ – Xander Henderson Jul 24 '18 at 22:59
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    $\begingroup$ @Xander, I'm not in it for the upvotes. I objected to a user posting a question and then deleting it when it got an answer, as I agree with a moderator that such an action is an abuse of the site. Once the question was undeleted, I took the opportunity to improve my answer, in response to a comment from another user. What's wrong with that? I'm not asserting anything about the lasting value of the question or the answer, other than the answer being fuller now than it was. The answer may help someone coming along who is interested in sums of two squares modulo a prime. Fire away. $\endgroup$ – Gerry Myerson Jul 24 '18 at 23:30
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    $\begingroup$ @GerryMyerson: it isn't pleasant to see one's own answer deleted, but in this case the question is clearly not up to many users' standards, so I think it is not surprising to see it deleted. At this point, the question is no longer deleted by the OP, but by several other users. $\endgroup$ – Carl Mummert Aug 5 '18 at 21:06
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    $\begingroup$ @Carl, it isn't pleasant to see any answer with nonzero mathematical content deleted. More to the point, I would not have put the question up for undeletion, had it been deleted by votes of users. My objection was to OP abusing the site by deleting the question after getting an answer. I thought that was clear. $\endgroup$ – Gerry Myerson Aug 5 '18 at 23:09
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Reopened

2 reopen votes left please:

Prove $ \lim_{z \rightarrow z_o} f(z) \in \mathbb{C}$ if $\lim_{z \rightarrow z_o} (z-z_0) f(z) = 0$

I made a new question, where I tried to be as clear and narrow as possible.

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Undeleted, redeleted, undeleted again, reopened

Statements that look obviously false but cannot be disproved. is at $+15$, and has answers at $+7,+10,+14,+20,+21,+8$, and $+15$. Please consider voting to undelete. [In the interests of transparency, I note that the $+15$ answer is mine.]

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    $\begingroup$ I agree that the question is highly upvoted and has highly upvoted answers. That does not make it an appropriate question for MSE. With regard to what is on-topic, it isn't a problem or puzzle, and I see no clear indication that there is a particular topic that needs to be clarified. With respect to what not to ask, the question seems designed to engender discussion, not to seek explanation. $\endgroup$ – Xander Henderson Sep 27 '18 at 16:35
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    $\begingroup$ For the benefit of the people who cannot see deleted questions, I'll add that this MO question is mentioned in comments: The most outrageous (or ridiculous) conjectures in mathematics. (Even if this one does not get undeleted, the linked MO post might be interesting for people who would consider Statements that look obviously false but cannot be disproved interesting.) $\endgroup$ – Martin Sleziak Sep 28 '18 at 8:42
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    $\begingroup$ @XanderHenderson Just curious, what would you then consider as on-topic for the soft-question and big-list tags? $\endgroup$ – dxiv Oct 4 '18 at 5:51
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    $\begingroup$ Surely we have better things to do that relitigate this post over and over again, and remove the collective efforts of 16 people. I see no harm from the existence of this post, except for the ruffled feathers of people who are inclined to overmoderation. $\endgroup$ – user296602 Oct 4 '18 at 22:13
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    $\begingroup$ In my opinion, if some want content and others do not then it should stay. The veto should be over removal rather than the converse. I will never understand why it's so important to wreck somebody else's party. $\endgroup$ – user334732 Dec 1 '18 at 18:22
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Reopened


There have been at least five questions asking how to prove instances of the general proposition $\log_m(m + 1) > \log_n(n + 1)$ for integers $n > m > 1$:

1. How to know if $\log_78 > \log_89$ without using a calculator? (3 May 2012), with an exemplary answer by user22805.

2. Logarithm inequality problem: $\log_2 3 > \log_3 4$ (27 Sep 2016).

3. Compare $\log_34 $ and $\log_45.$ (24 Mar 2017).

4. How to compare logarithms $\log_4 5$ and $\log_5 6$? (25 Sep 2018).

5. Comparing $\log_5 6$ and $\log_6 7$ (9 Oct 2018).

There have been at least three other questions asking to prove inequalities of the form $\log_a{b} > \log_c{d}$ for integers $b > a > 1$ and $d > c > 1$:

6. Which is bigger among (i) $\log_2 3$ and $\log _3 5$ (ii) $\log_2 3$ and $\log _3 11$. (9 Jun 2013).

7. How can I compare $\log_2 3$ and $\log_3 5$ without using a calculator (5 Sep 2017).

8. Comparing $\log_2 3$ to $\log_3 5$ (6 Mar 2018).

There has also been at least one more complex question in the same broad category:

9.Prove $\log_{\frac{1}{4}} \frac{8}{7}> \log_{\frac{1}{5}} \frac{5}{4}$ (20 Sep 2012).

Most recently, the following question was posted, but it was quickly closed as a duplicate (I confess to being one of those who voted to close it):

10. Comparing logarithms with different bases (23 Oct 2018).

The close message for question 10 reads:

This question already has an answer here: How to compare logarithms $\log_4 5$ and $\log_5 6$? 6 answers

But the only method used to answer a previous question (1-9) that can also be applied to the present question (10) is to find positive integers $m, n$ such that $b^n > a^m$ and $d^n < c^m$ (as in Eudoxus's theory of proportion), so that $\log_ab > \tfrac{m}{n} > \log_cd$.

In a comment (which has now been incorporated into the text of the question), the questioner showed that he was aware of this method, and had already used it to answer his own question. He continues:

However, that method doesn't work for every example, and I wonder if there's a easier way to solve this?

Strictly speaking, any logarithm comparison question could be answered in this way. But that is not always very practical, because one one has to search for suitable values of $m$ and $n$, which may be quite large. Some previous answers state or imply the general rule that $\log_a{b} > \log_c{d}$ if $\tfrac{b}{a} > \tfrac{d}{c}$ and $a < b$, but that rule does not apply in this case. It is interesting to ask if some other rule might be applied, eliminating the need for a possibly haphazard search for $m, n$. Failing that, ad hoc solutions to the present problem are also of interest.

Question 10 meets MSE's selection criteria, so it ought to be reopened.

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    $\begingroup$ The question lacks contract in any event. Most importantly: why were the specific constamts in the problems chosen? If the problem is about arbitrary constants, it should be rewritten to say so. If the OP was already aware of a method to solve the problem, that context should also be in the post. Overall the post does.noy seem to demonstrate much effort to write a good post. $\endgroup$ – Carl Mummert Oct 28 '18 at 16:19
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    $\begingroup$ @Carl On that basis, Diophantus would have a hard time posting a question here! Where, in MSE's rules, does it say that every question must be framed in the most general terms possible? What is wrong with asking a question about particular numbers? Especially as no-one has (yet) posted a general answer or a general question covering this particular case. Finally, even if it were granted (purely for the sake of argument) that an experienced user ought to have asked a more elaborate question, shouldn't a new user be cut some slack? $\endgroup$ – Calum Gilhooley Oct 28 '18 at 16:28
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    $\begingroup$ @Carl Also, it was closed as duplicate, and my point is that it is not a duplicate. The close message is a false statement, and the close decision should be reversed. (Of course, anyone can also vote to close it for another reason, and no such person need feel obliged to vote for reopening.) $\endgroup$ – Calum Gilhooley Oct 28 '18 at 16:34
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    $\begingroup$ !Calum: there's no problem posting a question with specific numbers - but it is up to the OP to include adequate context, and the reason for choosing seemingly arbitrary numbers is (in my opinion) part of that context. If this was asked person to person at a department tea, we would expect the asker to say something about the numbers involved. The OP should be encouraged to improve the problem, they have plenty of "slack" to do so. $\endgroup$ – Carl Mummert Oct 28 '18 at 21:19
  • $\begingroup$ I think my guilty conscience over this has now been assuaged. :) $\endgroup$ – Calum Gilhooley Oct 29 '18 at 0:36
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Undeleted

I nominate Optimization problem for routes for undeletion because the question asker self-deleted his question shortly after receiving an answer.

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  • $\begingroup$ Is that the right link? The question asker is named Jacob, which I take to be a male name, and the question was undeleted at the same time as this answer was posted. $\endgroup$ – Gerry Myerson Feb 6 at 21:03
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    $\begingroup$ @GerryMyerson Nice catch! I was typing on 📱, and I made this careless mistakes. I'm going to update this status of my answer. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Feb 6 at 21:08
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Reopened

Please consider reopening Is there an injective homomorphism from $S_4$ to $GL(2,C)$ because the question asker has shown efforts in solving the problem, and it has a score of 4 with an accepted answer of score 3 from a 25k user.

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    $\begingroup$ Answers should not be used to judge whether a question should be reopened. But in this case, the asker did include sufficient context, so that's irrelevant. $\endgroup$ – user21820 Mar 25 at 9:44
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    $\begingroup$ "Answers should not be used to judge whether a question should be reopened." That's your opinion, @user – it is not a rule, or even a consensus. $\endgroup$ – Gerry Myerson Mar 25 at 11:51
  • $\begingroup$ @GerryMyerson: It is your comment that is an opinion; it's not even a consensus. Both this and this clearly demonstrate a consensus that "bad questions beget bad questions" and "closed questions can and should be deleted even if the have good but standard answers; only truly great answers should rather not be deleted". $\endgroup$ – user21820 Mar 25 at 12:37
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    $\begingroup$ @user21820 Thanks for your comment. I'll be aware of that next time. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Mar 25 at 16:39
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    $\begingroup$ @user, your quote refers to deletions, not closure/reopening; what's more, the part that says "only truly great answers should rather not be deleted" plainly contradicts your assertions that "answers should not be used to judge...." $\endgroup$ – Gerry Myerson Mar 25 at 21:51
  • $\begingroup$ @GerryMyerson: Firstly, if a bad question ought to be deleted, then obviously it should not be reopened. Secondly, it would be real silly to assume that everything I say is to be taken completely rigidly with no room for exceptions; from my very first comment I meant that as a rule of thumb answers should not be used to judge... $\endgroup$ – user21820 Mar 26 at 5:43
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    $\begingroup$ @user, I'm not sure how I am to tell which things you write are to be taken completely rigidly, and which allow room for exceptions. Maybe we could work out some signal, so in the future I'll be able to tell. $\endgroup$ – Gerry Myerson Mar 26 at 8:51
  • $\begingroup$ @GerryMyerson: Usually, I try to be precise, using words like "typically" or "almost always" but, you know, that that is very tiring to do in every single statement. How about you just assume that there may be rare exceptions unmentioned unless I use the word "absolutely"? I don't think anyone is 100% precise all the time anyway, so that works for interpreting others' comments too. $\endgroup$ – user21820 Mar 26 at 8:59
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Reopened

Please reopen Am I have right answer about dual problem? since OP has responded to the comment and used MathJax to type out the math. In the revised version, OP has attempted to construct the dual program of the primal program, so it's OK for reopening.

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Reopened

I nominate A question of arithmetic regarding erection cost of a structure. for reopening since the question asker has shown his/her work in solving the problem.

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    $\begingroup$ I agree, but think they should also be encouraged either to edit what they said in comnents into the question, or to give someone else permission to do so. $\endgroup$ – timtfj Feb 5 at 12:20
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Undeleted, reopened

Please consider undeleting this old post: Show that a function $f:P(X)\to P(X)$ preserving the subset relation has a fixed point

It was created on Sep 17 '16, has two good answers.

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    $\begingroup$ It seems to be a special case of this question, and Aloizio's anwer in fact answers the general question. So if the goal is to preserve answers, the logical thing to do would be to move them there. $\endgroup$ – Arnaud D. Jun 28 at 13:48
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    $\begingroup$ It seems to me the Question at issue here has the more general formulation (it does not require an "increasing" function). In any case I've voted to reopen as the Question at issue meets my threshold for context (and it otherwise also on-topic). $\endgroup$ – hardmath Jun 30 at 19:45
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    $\begingroup$ I disagree with your assertion that the question has two good answers. It has one good answer, and a hint. The question itself is not good at all. I am content to see the question left undeleted, but I see no reason to reopen it. Arnaud D.'s suggestion is, I think, preferable. $\endgroup$ – Xander Henderson Jun 30 at 23:51
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    $\begingroup$ "I am content to see the question left undeleted." Well, that is what my proposal is. I agree that the question itself was not good enough and thus I did not ask for reopening. @Martin Sleziak has added useful information to the post. (Thanks!) Also, Aloizio's good answer mentions at the beginning "the nice answer by @Brian". $\endgroup$ – Jack Jul 1 at 1:47
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Undeleted.

Please consider undeleting: How to count the number of good permutations?

This is not a duplicate and has a good answer.

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Undeleted, deleted, undeleted, reopened

Please consider undeleting this post: What is the formula of this angle?

There is a well written and well-received answer to this interesting question.

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Undeleted

Please consider undeleting this post: How to evaluate $\lim_{x \to 3} (x^2-5x+4)^{x-3}$, which is clearly not a zero-effort question.

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Please consider undeleting and reopening this post: radical center of three circles.

This post clearly indicated an attempt and has a detailed answer.

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Undeleted, deleted, undeleted, deleted, undeleted

Please undelete this post Map subset of a group to zero?

This is not a trivial exercise. It has a very detailed thoughtful answer by @Arturo Magidin.

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    $\begingroup$ If you plan to keep saying things like "Redeleted (6/17/19) by a same group of users. One initiated three times the delete votes and one voted three times to delete this post. – Jack Jun 17 at 22:01" you might refrain from voting to undelete repeatedly, especially on posts where there was not recast delete vote prior to that. (There is now though.) $\endgroup$ – quid Jul 13 at 15:43
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    $\begingroup$ There has been no action whatsoever (to my knowledge) from mods or the system to prevent casting/initiating deletion votes for some particular posts over and over again by mostly same group of users. It is not difficult to count such instances. I assume from such observation that repeated voting is not discouraged in general. "If you plan to keep saying things like" This is an absurd and highly misleading comment from a moderator: your quoted comment refers to one particular proposal and I have never said it somewhere else. $\endgroup$ – Jack Jul 13 at 18:09
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    $\begingroup$ I take it you do not plan to keep saying things like the one I quoted, then. Well you did say "On the other hand, what one can see from the timeline is that a user voted to delete the posts twice while there are people who hold different opinions have already voted to undelete and reopen the post." which also raises double-voting in a critical way. $\endgroup$ – quid Jul 13 at 18:57
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    $\begingroup$ There has been no action whatsoever from mods or the system to prevent casting/initiating undeletion votes for some particular posts over and over again by mostly same group of users either. $\endgroup$ – Jyrki Lahtonen Jul 14 at 16:26
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Deleted, undeleted, deleted, undeleted, deleted, undeleted, reopened, closed as duplicate, deleted

What OP wrote under the problem statement clearly show his/her thoughts:

How can I do this if I don't know how $a_n$ is defined? I can use the given limit to get the range of $a_n$ in terms of $L$, but I lack the direction to complete the proof.

This is not a zero effort question. Please consider undeleting this post:

Given positive sequence $a_n$ where $\lim _{n\to \infty} a_n = L, L >0$, prove that $\lim_{n \to \infty} 1/a_n = 1/L$

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    $\begingroup$ Did you check if it's a duplicate? It's a very standard question. $\endgroup$ – quid Apr 26 at 14:32
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    $\begingroup$ @GerryMyerson a question might be eligible for closure for multiple reasons. It's maybe not a PSQ in it's purest form, but it's still not a good question. I'd say if somebody wants to restore a question it's on them to make sure no reason applies not just the one that was chosen. Further, it would have been on the asker to make some good faith effort to find a dupe before answering (and then complaining that their answer was removed). If a dupe of this question is not findable what does this tell about the level of organization in those tags. The priorities are not good. $\endgroup$ – quid Apr 27 at 7:12
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    $\begingroup$ @GerryMyerson here math.stackexchange.com/questions/1171733/… it was pretty trivial to find. $\endgroup$ – quid Apr 27 at 7:22
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    $\begingroup$ Well, in any case they complain. We can replace the "that" by "after". On the rest, again the onus is on them. They ought to explain that there is no dupe (supposedly). Further, it is generally considered as good form to mention if one has answered oneself. Especially if it is the only answer. @GerryMyerson $\endgroup$ – quid Apr 27 at 7:26
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    $\begingroup$ @GerryMyerson not sure about that. I might have had the luck to use the better strategy for that example, searching for words via Google on this site not for formulas for example 'convergence of inverse of convergent sequence' works well. $\endgroup$ – quid Apr 27 at 7:31
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    $\begingroup$ @GerryMyerson (and quid) I did try to find a duplicate and I indeed noticed that limit of reciprocal of a sequence away from zero should be a rather standard exercise in calculus/analysis and should have been asked before. However, I think "context" counts as an integral part of a post, and that is why we insist on "contexts", don't we? [cont.] $\endgroup$ – Jack Apr 27 at 13:14
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    $\begingroup$ [cont.] I am not able to find any same/similar confusion ("How can I do this if I don't know how $a_n$ is defined?") in any known post, for instance in the linked post in one of quid's previous comments and thus I do not think this post should be considered as an "absolute" duplicate that one should delete it. $\endgroup$ – Jack Apr 27 at 13:14
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    $\begingroup$ I agree with Jack's comments above, I don't think this post should be closed if a duplicate is not found where the same confusion is addressed. To the best of my knowledge, this confusion has not been addressed before, so this post should be undeleted and reopened. $\endgroup$ – Brahadeesh Apr 28 at 5:43
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    $\begingroup$ @GerryMyerson Basically a duplicate, except it doesn't require $a_n$ to be a positive sequence, was asked fairly recently at Sequence Limit Reciprocal Law Proof, where I provided an accepted answer. As for finding it, note it originally only used the tag "elementary-number-theory", but I changed it later to "limits", so searching for it initially might not have turned it up. However, I can't see the original deleted question content, but the page it brings up shows $2$ other somewhat related ... $\endgroup$ – John Omielan May 2 at 8:08
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    $\begingroup$ (cont) questions: Given: $\lim\limits_{n\to\infty}a_n=0$ prove $\lim\limits_{n\to\infty}\frac{1}{a_n}=\infty$ and How to formally prove that if $\lim \limits_{n \to \infty}a_n=\infty$, then $\lim \limits_{n \to \infty}\frac{1}{a_n}=0$.. Although they're somewhat different, and I haven't checked them carefully, I suspect their techniques are transferable. $\endgroup$ – John Omielan May 2 at 8:09
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    $\begingroup$ The status of the question had not changed at all. What is the justification for this edit? $\endgroup$ – quid May 31 at 16:57
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    $\begingroup$ On the comments above, which I only see know, due to lack of a notification, that's not a particular confusion. Any generic proof will necessarily do just fine to address this. I mean the proof you gave is completely generic. What do you think you did to address whatever specific confusion? $\endgroup$ – quid May 31 at 17:04
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    $\begingroup$ I agree with Brahadeesh's comment and I've undeleted the question. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Jun 14 at 9:21
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    $\begingroup$ @GNUSupporter8964民主女神地下教會 what is the particular confusion and how is it addressed specifically? $\endgroup$ – quid Jun 15 at 22:34
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    $\begingroup$ @quid The quoted question in Jack's last comment answers your first question; point (3) in Jack's answer addresses your second one. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Jun 16 at 3:17
0
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Reopened


Please consider reopening Indian Mathematicians. The question was closed as off-topic, apparently because of the existence of the History of Science and Mathematics site.

As I pointed out in a comment, first, questions about history of mathematics are on-topic here. The tag has almost two thousand questions and a decent amount of recent activity.

Second, the quality of many interactions at the HSM site is sadly rather poor (I was very enthusiastic about it when it started, so this poor quality quite bothers me), and it may end up being a disservice to send this question there.

(I would actually love to see the quality at that site to raise uniformly, and hope it happens relatively soon. But that is another matter.)

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  • $\begingroup$ I think at least the formulation of the question should be clarified a bit before it is reopened. The first answerer already misunderstood it. $\endgroup$ – quid Aug 30 '18 at 21:11
  • $\begingroup$ Fair enough. I'll do a slight edit. $\endgroup$ – Andrés E. Caicedo Aug 30 '18 at 21:16
  • $\begingroup$ I had decided to do an edit myself. Sorry for the confusion. I'll check back in one or two hours. If it's still closed then I'll give the final vote(s). This allows also for further editing. $\endgroup$ – quid Aug 30 '18 at 21:19
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    $\begingroup$ No problem. I gave the edit a second pass. (And thank you.) $\endgroup$ – Andrés E. Caicedo Aug 30 '18 at 21:22
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Undeleted, deleted, undeleted, deleted, undeleted, reopened, closed, locked, unlocked, deleted, undeleted, locked (for historical significance).

I think this question should be reopened. Thank you!

The original poster looked for the possibility to use the substitution $t=\tan\frac{x}{2}$ and he got a number of solutions.

By the way, the first comment of Lord Shark the Unknown is nothing. At the least, it gives a very complicated solution which the topic starter tried to apply but without success.

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    $\begingroup$ Quote from the question: "I tried tangent half-angle substitution but it became too complicated." First comment on main: "Try half-angle substitution, but with a little more determination. – Lord Shark the Unknown Aug 9 at 9:54" Answer by the OP: [DNE]. $\endgroup$ – Did Sep 8 '18 at 22:17
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    $\begingroup$ "By the way, the first comment of Lord Shark the Unknown it's nothing" Pfff... $\endgroup$ – Did Sep 8 '18 at 22:44
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    $\begingroup$ And now there's a rollback war. $\endgroup$ – Gerry Myerson Oct 1 '18 at 12:35
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    $\begingroup$ This question feels like a joke that everyone gets but me. (1) Why is this question particularly bad? The OP said they tried the obvious thing but to no avail. Presumably they made a mistake, but so what? That doesn't invalidate the question. (2) Why is there such a fierce edit/close/delete war? The question is 2 months old - let it rest!!! $\endgroup$ – user1729 Oct 12 '18 at 17:11
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    $\begingroup$ Rollback to Revision 9 by Alex Francisco, rollback to revision 10 by Michael Rozenberg, rollback to 9 by Alex, back to 12 by Michael, to 9 by Alex, to 14 by Michael, to 9 by Alex, to 16 by Michael. Crazy! $\endgroup$ – Gerry Myerson Oct 15 '18 at 22:44
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    $\begingroup$ Please, Michael, please, please, please stop editing the tags on that question. Enough already! $\endgroup$ – Gerry Myerson Nov 6 '18 at 11:08
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    $\begingroup$ This is just sorta embarrassing to watch at this point. And it's already back to 2 undelete votes, so I expect another full cycle in the next day. $\endgroup$ – user296602 Nov 27 '18 at 18:28
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Undeleted, reopened

I humbly request undeletion and reopening of this question, if you see fit to do so, because

a) reasons for closing should be derived from the question itself and not from speculation about the skills of the asker.

b) the given reasons for closing are incorrect - while the question sails close to an open problem, it asks a different but related question - it asks if the open problem (which relates to a series of polynomials) can be extended to its limit point.

c) the time from entering the reopen queue to deletion was less than two hours, denying any who might have been interested in its reopening the opportunity to declare the same.

d) moreover, I think others will find the question and any prospective answers of interest and value.

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    $\begingroup$ The time from entering the reopen queue to deletion may have been short, but the question had been on hold for five days already. As for the close reasons, I'll note that 2 of the close voters did not use "not math". I think that personnally I would have probably voted to close as unclear what you're asking, because on a first reading I honestly had no idea what you were talking about. $\endgroup$ – Arnaud D. Dec 1 '18 at 12:43
  • $\begingroup$ @ArnaudD. Yes, but the reopen request followed an edit which increased focus on the actual question and removed the motivation for it, when I believe the question's motivation was almost certainly the cause for the down votes and closure in the first place, rather than the question itself which stands alone. $\endgroup$ – user334732 Dec 1 '18 at 12:47
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    $\begingroup$ By the way, I think the most recent edit on your question (post-deletion) already makes the question more interesting. It only consists of adding a Wikipedia link, but that link already explains some of the context better than your question (for example, I hadn't realized that you were talking about polynomial bijections $\mathbb{N}^k \to\mathbb{N}$, but maybe that's just me). $\endgroup$ – Arnaud D. Dec 1 '18 at 12:57
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    $\begingroup$ For what it's worth, the reopen review was completed before the deletion, as one can see here. $\endgroup$ – Arnaud D. Dec 1 '18 at 13:15
  • $\begingroup$ @ArnaudD. good point, although predominantly the same users. Is there a better review link that shows timings etc.? I thought I saw one before but can never re-find it. $\endgroup$ – user334732 Dec 1 '18 at 13:39
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    $\begingroup$ There's the timeline, but I don't know if it is as detailed as you'd want. (By the way, there's another question about how to find it). $\endgroup$ – Arnaud D. Dec 1 '18 at 13:44
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    $\begingroup$ Setting aside all other issues, there are some obvious (and, I think, easily correctible) errors in your question's key equation, stating the F-P conjecture: the right hand side has no $y$ in it, and the index of summation $n$ appears nowhere in the expression being summed. I'm pretty sure you want the summation to go from $k=1$ to $n$, not $n=1$ to $k$, with $f_n(x_1,\ldots,x_n)$ on the left hand side, not $f_k(y)$. $\endgroup$ – Barry Cipra Dec 1 '18 at 15:28
  • $\begingroup$ @BarryCipra thank-you. I think I intended $y$ to be the set $\{x_1,x_2,\ldots x_k\}$ and yes, I agree I appear to have exchanged an $n$ with a $k$ but alas no edits are allowed on a deleted post so I can't correct it :( $\endgroup$ – user334732 Dec 1 '18 at 18:17
  • $\begingroup$ @RobertFrost That's surprising. In any case, I've just done the correction. $\endgroup$ – Arnaud D. Dec 1 '18 at 18:57
  • $\begingroup$ @ArnaudD. Thanks and you even got the $f_n$ I thought might get missed. $\endgroup$ – user334732 Dec 1 '18 at 19:00
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    $\begingroup$ What do you mean by "timings"? The time of the review is there exactly. As usual, hover over the time stamp to get a resolution to the second. $\endgroup$ – quid Dec 1 '18 at 23:44
  • $\begingroup$ @quid thank-you. That probably covers it although I can only see a deleted post on desktop so I'll have to check later $\endgroup$ – user334732 Dec 2 '18 at 4:07
  • $\begingroup$ @ArnaudD. Thank-you for the edit. A reopen vote would be greatly appreciated (only if you think it appropriate). Else the deleters will reverse the undeleters! $\endgroup$ – user334732 Dec 3 '18 at 10:39
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Can this answer (on permutation groups) be undeleted:

https://math.stackexchange.com/a/3197094/10513

It was deleted for not providing an answer to the question. However, it gives a decent hint which leads to a solution. The hint is essentially "consider odd vs. even numbers". This was made formal in the accepted answer, which used mod 2.

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  • $\begingroup$ I think it's a bit of a stretch from that hint to the accepted answer. The hint ought to be a comment (in my opinion). $\endgroup$ – Gerry Myerson Apr 29 at 12:50
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    $\begingroup$ @GerryMyerson Hints are a grey area. But I don't think deleting them because they are "a bit of a stretch" is the right thing to do. $\endgroup$ – user1729 Apr 29 at 12:55
  • $\begingroup$ It would have been better, had a moderator converted the "answer" to a comment. You could try flagging the question for moderator attention, and making that suggestion. $\endgroup$ – Gerry Myerson Apr 29 at 12:59
  • $\begingroup$ I flagged it beforehand, and was told to post my request here (admittedly i didn't suggest making it into a comment) $\endgroup$ – user1729 Apr 29 at 13:19
  • $\begingroup$ OK, now you know what to do. $\endgroup$ – Gerry Myerson Apr 29 at 13:22
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Undeleted, Merged and then deleted

Please reopen https://math.stackexchange.com/q/3208119/290189 since OP has self-deleted his/her own post after getting an answer. The community should have been given enough time to vote.

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    $\begingroup$ You can't reopen a question that isn't closed, GNU. Now it has been closed, as a duplicate, but I don't see how $x^y+y^x=(xy)^2-19$ is a duplicate of $x^y-y^x=xy^2-19$. So, I'm flagging for moderator attention. $\endgroup$ – Gerry Myerson Apr 30 at 13:47
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    $\begingroup$ @GerryMyerson By the moment I posted this answer, I did voted to close this question as missing context. I did notice the difference between the two. Thanks for reminding me. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Apr 30 at 13:52
  • $\begingroup$ @GerryMyerson a problem is that the original version of the question was incorrect. A third party edited it to this version, while main OP had re-asked a different version. $\endgroup$ – quid Apr 30 at 15:32
  • $\begingroup$ I deleted it after the merge now. This did not work out ideally, but it's near impossible to fix. If somebody wants that version of the question on the site I recommend to ask it anew. $\endgroup$ – quid May 2 at 18:17
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Deleted, undeleted, deleted, undeleted, reopened

Please reopen Calculating the summation$\sum_{n=1}^{\infty}\frac{H_{n+1}}{n(n+1)}$ because it's not an elementary question and OP has tried checking the proposition using Wolfram Alpha.

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    $\begingroup$ In my opinion it's very poor style to reignite this after month without mentioning any of the earlier activity in which you even were involved. Thus, I locked the post for now. $\endgroup$ – quid Apr 30 at 11:43
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    $\begingroup$ I'm puzzled. A "content dispute" notice was lifted in March 2018. The content has not been altered since then. So it seems strange to lock it for "content dispute" now, @quid. [I guess I should mention that I was involved in earlier activity.] $\endgroup$ – Gerry Myerson Apr 30 at 13:56
  • $\begingroup$ @GerryMyerson Are your really puzzled or are you just searching an argument? First, the content of the post was also not changed between the first locking and the first unlocking. Second, the lock was not lifted in the sense of somebody lifting it, it simply expired. It was not reinstated as there seemed no need back then about a year ago. Then half a year ago, there was one more round of undelete-delete but it fizzled out quickly. Now somebody wants to go back to this again, indeed without any further changes, simply picking up the del-undel again. To prevent this, I locked it. $\endgroup$ – quid Apr 30 at 14:36
  • $\begingroup$ Third, it might be relevant to note that the lock was "lifted" while the post was deleted. Thus, if consistency is the concern of course I should lock it again now. I could also have it become undeleted and then personally delete it again. Last time around some where keen on locks being used. So, there you go. Of course that's not fine for you now either, presumably because it does not cater to your personal preferences. $\endgroup$ – quid Apr 30 at 14:43
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    $\begingroup$ To sum up, I locked it to prevent the delete-undelete cycle being restarted. By now the question was deleted four times. Plus it is an odd situation, in that it first got siginificantly improved by a third party only for this then being undone If anything should happen likely a completely new version should be posted. This would be a reasonable thing to do if preserving content is the actual goal. Of course if playing un-del games should be the goal... thus locked. @GerryMyerson $\endgroup$ – quid Apr 30 at 14:48
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    $\begingroup$ @quid, when I write that I am puzzled, please do me the courtesy of accepting that I really am puzzled. I'm puzzled not so much by the locking but by the phrase, "Content dispute", when there was no change in content. Had the locking notice said "Prevent delete/undelete cycle" I don't know that I would have made any comment. Does a moderator have the option of inserting custom-made locking notices, or is "Content dispute" the only phrase available? Also, I always assumed that when a moderator locked a question, the question stayed locked until a moderator decided it was time to unlock it.... $\endgroup$ – Gerry Myerson Apr 30 at 22:46
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    $\begingroup$ ....I didn't know that locks expired of their own accord after a week. I've been here almost a decade, and I'm still learning how the place works. $\endgroup$ – Gerry Myerson Apr 30 at 22:47
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    $\begingroup$ @GerryMyerson the list of reasons is fixed (we can ask for additions in principle but not spontaneously) "content dispute" is the one commonly used in this case, others are "off topic comments", "contest question", "cw answer", "historical significance". We can lock for an hour, for a day, for a week, or permanently. Usually one tries to avoid permanent locks. $\endgroup$ – quid Apr 30 at 23:58
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    $\begingroup$ Probably it's worth mentioning that there already is one answer in this thread about the same question. $\endgroup$ – Martin Sleziak May 15 at 7:34
  • $\begingroup$ @quid, thanks for the explanation about length of locks. It's not possible, is it, for non-moderators to see what length a moderator has chosen when that moderator locks a question? $\endgroup$ – Gerry Myerson May 20 at 4:26
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    $\begingroup$ @GerryMyerson indeed I think that's not possible. $\endgroup$ – quid May 20 at 8:39
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Please unmark the duplicate of this question. I have clearly said that my question has nothing to do with duplicate one. I am asking totally different thing and the duplicate question's answer does not help me at all. It is also an unique question which follows m previous question.

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  • 3
    $\begingroup$ I don't believe the relationship between the Questions is quite so simple as one "has nothing to do with" the other. Both involve intersections between two spherical caps, although you might not have visualized your problem in this way. There might still be a further problem in stating the area in terms of how you parameterized the spherical region, I grant, but it would be worth understanding the solution of the proposed duplicate to try restating the area given there in your terms. $\endgroup$ – hardmath Jun 6 at 17:11

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