# Requests for Reopen & Undeletion Votes (volume 07/2018 - 12/2020) [duplicate]

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 is closed pushes the question into the reopen review queue if the edit is done within 5 days of closure, and so does a reopen vote. (If the review has already been finished, it is shown on the timeline of the question.) When 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 the information Reopened or Undeleted at the start once the request has resulted in some action. (If the action is undone, add this too, like Reopened, Reclosed.)

• Do not only post a request, like "request reopening of link". 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 it in a way that takes the feedback the post received into account positively 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 CURED is a reasonable place for such requests. The same guidelines apply there.

Earlier versions of this thread that served as a model:

• I edited the post inspired by a concern expressed in a comment. – quid Jul 19 '20 at 23:49

Undeleted, closed, deleted, undeleted, redeleted

I nominate Solve the recurrence $$\sqrt {x_n} − 5 \sqrt {x _{n−1} }+ 6\sqrt {x_{n−2}} = 0$$ for undeletion because OP has self-deleted his post shortly after receiving an answer. That's rude to the answerer.

• I agree that the question should not have been deleted by the original asker, and would have voted to undelete had I seen this before the question was undeleted. That being said, it is a pretty low quality question, and would like to now nominate it for closure and (if it is not improved) eventual deletion. – Xander Henderson Nov 12 '18 at 23:26
• @XanderHenderson Agreed and updated the status of my answer. – GNUSupporter 8964民主女神 地下教會 Nov 13 '18 at 1:27
• It is inconceivable this question is undeleted. Even the answer is pretty low-quality. – YuiTo Cheng Jun 26 '19 at 4:53
• I find that revision history really surprising : one (now removed) user voted to undelete and then close the question, OP initially self-deleted the question but 5 days later voted to undelete after the second deletion, and now you've voted to undelete and then redelete the day after. Pardon my French, but WTF? – Arnaud D. Jun 27 '19 at 9:31

Please consider undeleting this post: Integral $$\int_{0}^{2\pi} \ln (2\sin(\frac{x}{2}))dx$$

Whether the asker should articulate more details in "I've tried some substitutions" could be debatable for reopening the post; I do not think it should be deleted. There have been two answers, one of which has 11 upvotes.

• The question was on hold for a week without modification before it was deleted. The answers are fine, but standard, and don't rise to the level of exceptional. I see no reason to undelete this question. The asker clearly got what they wanted, and I don't see that question providing any lasting value to the site. – Xander Henderson Jul 2 '19 at 0:46
• The lasting value to the site, like many other posts, is that there are two good answers to a tricky calculus question, which is not only useful for the asker but also future readers. – user9464 Jul 2 '19 at 1:48
• The first part of your reply to me does not contradict what I said: you say that there are two good answers, I said that there are no exceptional answers. As to use to future readers: I disagree. This is a specific integral which can be analyzed using relatively standard techniques. The question itself is not terribly searchable (it is only going to come up if someone wants to deal with that specific integral (e.g. they are assigned the same problem as a homework exercise, and are trying to cheat), and the answers are not of any general interest (they are standard, but not general). – Xander Henderson Jul 2 '19 at 1:53
• Disagree. "This is a specific integral which can be analyzed using relatively standard techniques. ... the answers are not of any general interest " does not justify the deletion. MSE is not MO: most, if not all, of questions here "can be analyzed using relatively standard techniques". For instance, this recent question that has two good answers, the accepted one written in detail nicely by you, is a rather "standard" one. I would certainly not vote to delete such posts. (In case of any possible confusion: this is NOT sarcasm.) – user9464 Jul 2 '19 at 2:48
• It is funny that you pick that example. I downvoted that question, and voted to close it. It was not closed, and the other answers were, in my opinion poor answers (as they failed to address the key point, which is that an induction proof is needed somewhere). If the question is not going to be closed and deleted, it should at least have a correct answer. I would still be happy to see that question closed, and would not object to its deletion---my answer is nothing special, and doesn't (IMO) rise to the level of exceptional. – Xander Henderson Jul 2 '19 at 2:56
• Moreover, applying standard results to a specific problem is very different from demonstrating the correctness of standard results then leaving it to the reader to apply that result to their specific problem. – Xander Henderson Jul 2 '19 at 3:01
• Well, (1) I have done my proposal for undeletion. Readers can make their own decisions. (2) I will object strongly the post I just mentioned being deleted, considering the quality of your exposition and egreg's good answer. (How do you find the review history by the way?) (3) ... have to leave now. – user9464 Jul 2 '19 at 3:13
• Probably a duplicate of one or more of math.stackexchange.com/questions/815762/… and math.stackexchange.com/questions/889902/… and math.stackexchange.com/questions/679233/… and math.stackexchange.com/questions/2656431/… and also comes up in any question containing the name "Clausen". – Gerry Myerson Jul 2 '19 at 3:20
• @Jack To find the review history I go to the timeline of the post and then click on the link to the review event there. I don't know if there's a quicker way. – user279515 Jul 2 '19 at 6:41
• @GerryMyerson: having read your links one by one, I would probably not called the post a duplicate of those, although they are related to the Clausen function. (Never known this before, thanks for mentioning it.) – user9464 Jul 2 '19 at 11:47
• @Brahadeesh: Thanks for that. One can indeed use math.stackexchange.com/posts/3143084/timeline – user9464 Jul 2 '19 at 11:56
• It's funny how those who voted to close/ delete are here on this site for a while, and even claim to know that the question is easily searchable. Yet, instead of trying to mark it as duplicate, they simply delete it. Also it's quite bold for a single group of people (CRUDE users) to decide that it has no value for this site. – Zacky Jul 22 '19 at 8:50
• @XanderHenderson I wrote above in the third person since you're not the only one who believes that, but since you commented it here, can you please tell me why haven't you tried to mark it as duplicate (if it's easily searchable) and simply decided to remove the content? (maybe there's a reason that I'm missing). – Zacky Jul 22 '19 at 8:58
• -> Before voting to delete, please check whether there are any good answers; if so, then the question should be flagged for moderator attention as a potential merge candidate. We don't like to lose great answers!. And the answers provided there are definetly good. Thus those who deleted it violated the "rule" that I copy-pasted. // A little off-topic, but I hope that you are aware that who asked the question couldn't care less if the question is deleted since he/she already took the informatio needed. Thus by deleting the question, it even helps that user instead of penalizing them. – Zacky Jul 22 '19 at 14:00
• -> Of course, the posts around here aren't only for those who asked, but for the whole community. I fail to see why there ins't a way to penalize the users (for example a "question ban" if the questions previously posted are bad), but instead the decision that CRUDE users took is to penalize the whole community by erasing good content. Anyway, it's pointless if I type here in the comments, soon I will try to make a meta post about something related to this. Thanks for your time and have a nice day! – Zacky Jul 22 '19 at 14:12

Undeleted, reopened

Please consider undeleting and reopening this post:

where OP gave his/her thoughts:

Honestly I have no idea about how to approach this problem. I tried the expansion of $$\sin x$$ on the left hand side and then expand $$\cos x$$ on the right but end up with a mess. Then again $$\cos x=(\sin x)'$$, but by converting each term on the right hand side into derivative of sine does not give any sensible identity to draw out something. Really out of ideas on this one. Is there any way to do this? Please give me some hints. Thanks for your time.

Undeleted, deleted, undeleted

Please undelete and consider reopening this post: Show this equation has every positive integer as solutions

OP did give his thoughts. NOT a no-context question. And there are two good answers.

Undeleted, deleted, 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.

• You say that the question should be opened because it is "clearly not a zero-effort question." This seems to imply that the question was closed because it "lacks effort". However, "lacks effort" is not one of the close reasons used on MSE. Indeed, I see that question was closed for "lacking context". For example, a description of what theory the asker is familiar with and what course they are taking. Are they expecting a computation involving $\varepsilon$s and $\delta$s? L'Hospital's rule? What? The question should be deleted. – Xander Henderson Aug 15 '19 at 12:31
• Moreover, examining the comments attached to that question, it is not even clear where the function being discussed is meant to be defined. Is it a real function with a very "hole-y" domain? or a complex function, in which case one needs to consider branches of the logarithm? It is not a good question. – Xander Henderson Aug 15 '19 at 12:34

Deleted, undeleted, deleted, undeleted, deleted, undeleted, reopened, closed as duplicate, deleted, undeleted

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 $$\lim_{n \to \infty} 1/a_n = 1/L$$

• Did you check if it's a duplicate? It's a very standard question. – quid Apr 26 '19 at 14:32
• @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. – quid Apr 27 '19 at 7:12
• @GerryMyerson here math.stackexchange.com/questions/1171733/… it was pretty trivial to find. – quid Apr 27 '19 at 7:22
• 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 – quid Apr 27 '19 at 7:26
• @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. – quid Apr 27 '19 at 7:31
• @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.] – user9464 Apr 27 '19 at 13:14
• [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. – user9464 Apr 27 '19 at 13:14
• 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. – user279515 Apr 28 '19 at 5:43
• @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 ... – John Omielan May 2 '19 at 8:08
• (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. – John Omielan May 2 '19 at 8:09
• The status of the question had not changed at all. What is the justification for this edit? – quid May 31 '19 at 16:57
• 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? – quid May 31 '19 at 17:04
• I agree with Brahadeesh's comment and I've undeleted the question. – GNUSupporter 8964民主女神 地下教會 Jun 14 '19 at 9:21
• @quid The quoted question in Jack's last comment answers your first question; point (3) in Jack's answer addresses your second one. – GNUSupporter 8964民主女神 地下教會 Jun 16 '19 at 3:17
• @GNU As detailed this ask nothing more than that the author understands that they might be able to do it or at least how to strat for a specific sequence like say $2n/(n+1)$. Any generic proof will do just fine, and what about the third point? Again any proof will have to address this somehow (in one based on continuity it might be hidden). Certainly it's findable in other answers. It's just a contrived argument to save this post, and frankly I am appalled by this. Explain how this answer math.stackexchange.com/a/1171755 is not sufficient or math.stackexchange.com/q/54754? – quid Jun 16 '19 at 8:51

Deleted, undeleted, deleted, undeleted, reopened, closed as duplicate

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.

• 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. – quid Apr 30 '19 at 11:43
• 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.] – Gerry Myerson Apr 30 '19 at 13:56
• @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. – quid Apr 30 '19 at 14:36
• 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. – quid Apr 30 '19 at 14:43
• 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 – quid Apr 30 '19 at 14:48
• @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.... – Gerry Myerson Apr 30 '19 at 22:46
• ....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. – Gerry Myerson Apr 30 '19 at 22:47
• @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. – quid Apr 30 '19 at 23:58
• Probably it's worth mentioning that there already is one answer in this thread about the same question. – Martin Sleziak May 15 '19 at 7:34
• @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? – Gerry Myerson May 20 '19 at 4:26
• @GerryMyerson indeed I think that's not possible. – quid May 20 '19 at 8:39

Please undelete this post: $$n^4 + 4^n$$ is a not a prime

OP clearly states context for his/her question:

This question appeared in the undergrad entrance exam of the Indian Statistical institute.

When $$n$$ is even the proof is simple. For $$𝑛=2𝑚+1$$ I am utterly stuck.

True that this is a duplicate of some previous posts, but duplicate can be useful. Moreover, it is not necessarily easy at all to identify this question as a duplicate:

• The useful searching engine Approach0 is NOT well known, neither it is mentioned on the page of help center of MSE.
• A quick search of the expression $$n^4+4^n$$ on the MSE searching box returns something irrelevant:
• If one posts this as a new question: the "similar questions" box does not show any one of the duplicate:

"Questions that are extremely off topic, or of very low quality, may be removed at the discretion of the community and moderators." This 5 upvoted one with three answers is not.

• At some point, every math student really ought to be shown the factorization of $x^4+4$. – Gerry Myerson Sep 26 '19 at 7:47
• This is an umpteenth reincarnation. Even in 2013 when André Nicolas answered it we had already covered it many times. Also, while duplicates were seen as somewhat useful back in 2013 (when Jeff Atwood's strangedupe comment was often cited), the site has moved on since. The most recent word from above (don't remember for sure whether it is from JA or the current CEO Joel Spolsky) reads: Over time duplicates become vast landmine fields. – Jyrki Lahtonen Sep 26 '19 at 16:24
• The sentence ("... landmine fields") Jyrki mentioned is from this article by Jeff Atwood. That one is specifically talk about StackOverflow, which is sort of the counterpart of MathOverflow. (cont.) – user9464 Sep 26 '19 at 17:18
• Jeff explicitly writes in that article the following : But I will point out that there is plenty of precedent on the Stack Exchange network for splitting sites into "expert" and "beginner" areas with slightly different rulesets. We've seen this for Math vs. MathOverflow, English vs. English Learners, Unix vs. Ubuntu... perhaps it's time for a more beginner focused Stack Overflow where duplicates are less frowned upon, and conversational rules are a bit more lenient? – user9464 Sep 26 '19 at 17:18
• I am not following SO much at all, but what little I have seen of it it is nowhere near the level of sophistication of MathOverflow (admittedly my observations are likely biased). But I would support walling off lower level math (like freshman and below) to a Math Learner site. – Jyrki Lahtonen Sep 26 '19 at 21:49
• I don't get what's the contradiction even. Certainly duplicates will happen, some will be caught other won't be caught. Of those that do get caught we'll keep some that seems relevant as "sign posts" and we remove the rest without much ado (either way). Why would we want to keep them? – quid Sep 26 '19 at 22:26
• On search, searching n^4 + 4^n for works like a charm Why would one use strange spacing, or in any case just check one version, and include the completely irrelevant dollars? – quid Sep 26 '19 at 22:34
• @quid: your linked search of n^4 + 4^n , which does return a duplicate result, uses "strange spacing". If one searches n^4+4^n without the spacing before and after the plus sign, one would not see the charm. – user9464 Sep 27 '19 at 0:04
• The answers are all dupes of answers given many times in the past. This FAQ occurs many times every year. There is no need to keep adding duplicate answers every time it reoccurs. Doing so makes it difficult if not impossible for users to locate the most enlightening answers. – Bill Dubuque Sep 27 '19 at 0:45
• @Jack I forgot to add that Theoretical Computer Science is the StackOverflow analogue of MathOverflow. Don't get mislead by the inclusion of the word Overflow. If SO walls off a learners' site, we should do the same. – Jyrki Lahtonen Sep 27 '19 at 3:42
• And also, the voting already gives low level math an unhealthy advantage in the gamification aspects of the site. Simply because users are obviously not going to (and should not) vote on material over their head. You wanting to be more lenient about low level duplicates would exacerbate an already serious problem. – Jyrki Lahtonen Sep 27 '19 at 3:45
• Well, let's forget about which spacing is strange or not. One might learn the lesson that one should search for both variations. I'd still maintain that the spacing there is the more natural way to type it. But I am glad that you seem to agree now that the dollars are useless. // And even if it was completely unnatural it is the very spacing that was used in that post that you want undel too. Thus at least that user likely would have used the same spacing if they had searched and keeping this as a dupe would not even help future searches (except maybe via answer, but then merge could do). – quid Sep 27 '19 at 8:44

Undeleted, reopened

Please undelete and reopen this post: Evaluate this limit: $$\lim_{n \rightarrow \infty} \frac{n\sin n}{2n^2 - 1}$$

This post is by no means missing context. OP clearly stated at the beginning what he/she tried and where he/she got stuck. This post has also a detailed answer by a 50K+ user.

• It might be worth noting that unfortunately that so-called detailed answer completely ignores the provided context, in that sense it's a rather poor answer, but arguably that's tangential. I'd tend to agree that this question does show reasonable context. If we take the context into account, likely it's a dupe. – quid Sep 23 '19 at 15:52
• Instead of saying "what goes wrong with my thoughts" or "how can I go on with my original approach", OP explicitly stated that "Any help will be appreciated". And @Clement C. helped this user by directly giving an argument. Not a poor answer, and there have four people considering it good. This post is an extremely poor choice for deletion. – user9464 Sep 23 '19 at 15:58
• quid does make a fair point that an answer showing how OP could go on with the original approach may be more useful for the asker. One could add such an answer after this post is reopened. – user9464 Sep 23 '19 at 16:06

Reopened, undeleted, closed, reopened

Please consider undeleting this question where I also provided an answer: Integrating $$\int_0^1\frac{x\ln (1+x)}{1+x^2}dx$$ with restricted techniques.

The OP from clearly provides background on how the integral appeared, although it was some kind of homework now it can be useful for others too.

• It's good form to disclose that one has an answer on the post oneself. – quid Aug 15 '19 at 20:59
• Hope I don't sound rude, but I don't understand what you wrote even with translate. Did you meant: It's a good thing to mention that I posted an answer to the linked question? – Zacky Aug 15 '19 at 21:07
• Yes. You should mention this. It makes clear that you are not a neutral third party. You have a personal interest in the undeletion. This does not disqualify you from making the proposal. But it is good form to be upfront about it. – quid Aug 15 '19 at 21:12

Deleted, undeleted, deleted.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

The close notice for How to prove that the permanent of a doubly stochastic matrix is positive? says, "Add details and clarify the problem being solved. This will help others answer the question."

The problem being solved is perfectly clear (to anyone who knows what a doubly stochastic matrix is, and what the permanent of a matrix is), and others have not needed any help answering the question, so the close notice strikes me as invalid. Please consider voting to reopen this question.

• Possibly you did not get the memo: math.meta.stackexchange.com/questions/31147/… – quid Mar 5 '20 at 15:31
• @quid if a user is going to vote to close a question, and if none of the currently available close reasons applies, I reckon the user really ought to leave a comment explaining how the question doesn't measure up. What was done for this question, even if OP clicked to see the further information on "add details and clarify," gives OP no clue as to what to do. Heck, it gives me no idea as to what the close-voters actually had in mind. Let's reopen the question, and give the close-voters the chance to make their case. – Gerry Myerson Mar 5 '20 at 21:30
• Maybe that would have been better but there is only so much time and it fits well enough. As for you, it is hard to believe that you actually had not understood what the matter was (as opposed to disagreeing). Either way, I hope you keep the information obtained here in mind going forward. – quid Mar 6 '20 at 4:36

Deleted.

2 or 3 days ago, the question What's the connection between the Heegner numbers and 37? was asked.

(1). The first version of that question, was not eligible as a question to be asked in MSE, and I was the fifth user, who voted to close the question.

• User @David wrote that: 37 is the largest prime for which -163 is a quadratic non-residue.
• Then I pointed out that his comment is not right by this comment: Consider this Legendre symbol: (−163/137)=−1.
• Then he answered that: The statement is more like 37 is largest prime p s.t. All primes, q: 2<q<=p have (−163/q)=−1. I would like to state this correctly and succinctly.

(3). Why I was convinced that his question is a good question?

• His comment was interesting to me, because I've realized that the phenomenon, which he pointed out, is not accidental and is closely related to the properties of Heegner numbers. [Not important: As you can see in the comments; at first, I wrongly thought that it is related to Rabinowitz theorem. For proof of the Rabinowitz theorem see this answer by Will Jagy.]
• Definition: A Heegner number is a square-free positive integer $$d$$ such that the imaginary quadratic field $$\mathbb{Q}(\sqrt{-d})$$ has class number $$1$$. I wrote my answer, in the comments [see these six consecutive comments]. If we set this definition as the definition of Heegner Numbers, then the First case is just the immediate consequence of the definition. I mean whether we know the total set of Heegner numbers is finite or not, we can do the first case without any use of powerful theorems like Baker–Stark–Heegner theorem, just by the knowledge of $$19^{\text{th}}$$ century. [Very Important: Unfortunately, in the Second case, I strongly used the Baker–Stark–Heegner theorem. Not important: If we break the second case in some new cases, then the case "$$(\dfrac{-H}{q})=0$$ and $$q^2 \nmid (H)$$" can be done in a quite elementary manner, but yet I don't have any idea to do the case "$$(\dfrac{-H}{q})=0$$ and $$q^2 \mid (H)$$".]

(4). If a curious person sees that question, then probably he/ she would click on the show N more comments to see the comments. So Why do I insist to reopen that question? An unsatisfactory answer would be something like this: (A) Suppose that a random student who does not have enough curiosity about this special question, will see this question. (+) Since this question is closed for the lack of details, (++) and since there is not an answer for it; the most probable scenario would be that he/ she will be taught there is nothing special behind this question. (B) Another unsatisfactory answer would be something like this: From a pedagogical point of view: Someone else can write a better answer, maybe someone can be able to answer it without using any powerful theorems. Finally, reading a solution as a single answer is better to follow the separated comments. At last, I should confess whether this question reopens or not, it would not cause important changes.

(5): TOTALLY IRRELEVANT: As a math student, I should be careful about my counting: In my last comment, I wrote My 7th comment, but it was my eighth comment.

Let's set this definition as the definition of a Heegner number. As I stated in the comments, the question can be considered as

• Q($$1$$): Let $$H$$ be a Heegner number, then for any prime $$2 \neq q \leq \dfrac{1+H}{4}-2$$ we have $$(\dfrac{-H}{q})=-1$$,

Or equivalently:

• Q($$2$$): Let $$H$$ be a positve square-free integer, and let $$q$$ be a prime number $$2 \neq q \leq \dfrac{1+H}{4}-2$$, such that $$(\dfrac{-H}{q})=+1$$. Then $$H$$ is not a Heegner number.

Both of these equivalent questions are very surprising to me. Now consider this question:

• Q($$3$$): Let $$200 \leq H$$ be a positve square-free integer, then there exists a prime number $$q$$ such that: $$2 \neq q \leq \dfrac{1+H}{4}-2$$ and $$(\dfrac{-H}{q})=+1$$.

If I was able to prove the above question, then the Baker–Heegner–Stark theorem, would follow immediately. So Q($$3$$) is not an easy question.

• Reamrk($$4$$): Let $$\dfrac{49}{3} \leq H \stackrel{8}{\equiv} 3$$, then the Gauss's upper bound [Gauss's bound, is a better bound, than Minkowski's bound, for the norm of ideals to be checked in order to determine the class number of the imaginary quadratic field $$\mathbb{Q}(\sqrt{-H})$$], tells us: By considering Baker–Heegner–Stark theorem, if $$H \notin \{ 11, 19, 43, 67, 163 \}$$, then there is a prime $$q$$ such that: $$2 \neq q \leq \sqrt{\dfrac{H}{3}}$$ and $$(\dfrac{-H}{q})=+1$$. Note that for $$\dfrac{49}{3} \leq H$$ this new bound is surprisingly smaller than $$\dfrac{1+H}{4}-2$$. These were some parts of my unsuccessful attempts to prove Q($$3$$), without use of Baker–Heegner–Stark theorem.
• You ask, "Why do I insist to reopen that question?" and then you give two reasons, both of which you yourself label as "unsatisfactory". So, I'm confused. Do you have a satisfactory reason for insisting on reopening the question? (And, if so, can you give it without boldface and blockquote and all-caps and other annoying typographical flourishes?) – Gerry Myerson Jun 16 '20 at 23:58
• Dear @GerryMyerson , I used the word "unsatisfactory" for the first answer (A), because I wasn't sure about the opinion of the generic person, who would see that answer; and also I didn't have enough courage to say that answer is satisfactory to me. Also, I didn't add new comments to that question, since writhing long mathematical comments is very hard to me, because of the lack of the editor to be aware of my LaTeX mistakes, and also there is a restriction on the total number of characters. – Davood KHAJEHPOUR Jun 17 '20 at 6:28
• Dear @GerryMyerson , I accustomed to use bold and colorful formats, for the convenience of the reader; because to me, it plays the role of change of tone in the web environment. I didn't even think that it may be annoying; thank you for notifying this subject. – Davood KHAJEHPOUR Jun 17 '20 at 6:29
• @DavoodKHAJEHPOUR Can you please edit your post here down to the essential details? There is so much extraneous commentary in it that I cannot pick out the reason(s) why you think this question should be reopened. I'll note that the question has now been deleted. – Xander Henderson Jun 17 '20 at 13:58
• Dear @XanderHenderson Since this edit would be something related to a question, which is already deleted; I am afraid that if I continue editing my post here, then I will be punished because of some rules that I do not know. Since there is no guarantee that I will not be punished, I will not continue no longer; However, I believe that the answer to that question contained important things. – Davood KHAJEHPOUR Jun 17 '20 at 14:17
• @DavoodKHAJEHPOUR You will not be punished for editing your answer to make it more clear. If you believe that the question is worth saving, then you should clearly and concisely make your case. Three screenfuls of oddly formatted, rambling text is unlikely to convince anyone. – Xander Henderson Jun 17 '20 at 15:07
• @XanderHenderson If writing that question and its comments would be helpful, I will do this. Do you mean this? – Davood KHAJEHPOUR Jun 17 '20 at 15:54

Undeleted, Deleted, Reopened, Undeleted

• This inequality question is clearly a conjecture made from an existing question, which I think is a fair question to ask. Inequality conjectures on this site are often false. This is one of the rare cases where experiments yield correct claims. I expect that there are many inequalities that can be inferred from the inequality in question (such as this one, this one, this one, Comment 5 of this one, and even Comment 1 of this one). We should preserve it, to keep it a reference.

• The current answer (mine) is unsatisfactory, for it is long and too complicated. This is not an easy inequality problem, and there should be a better way to solve it. If my having posted an answer there is an issue for some users (which I don't understand why, it is not like reputations grant anything to me), I can make my answer a community wiki post. Knowledge, on the other hand, is precious (and reputations are not at all precious, which is perplexing to me because a lot of arguments here are based on reputations, e.g., reputation farming, who benefits from undeleting some posts, etc).

• This is not a contextless question. Users are often asked to provide a context, and the source of the problem is a context. The asker stated that this was modified from an old question. You might think this is insufficient. I disagree, but anyway, more context has been added.

• You should note that the question, which is a contextless problem statement question, currently has only one answer, which was written by you. You are not a disinterested third party in this case. – Xander Henderson Jul 2 '20 at 5:06

Undeleted, Reopened

I want this question to be to undeleted because I wrote a long answer for it and it was a correct and well-explained question. The question now has more context.

Edit: Can someone suggest for edits that should be made to reopen this post also? This problem is quite similar to Siegel's lemma and I don't think MSE has a post regarding such problems. I think it should be reopened also. Please consider this to be reopened.

• Thank you for being upfront about your reasons for wanting this question undeleted / reopened. Unfortunately, I do not feel that I can vote to undelete the question–the question is a "problem statement question", and does not meet the quality standards of Math SE. The asker has not provided any context, such as a source for the problem or any thoughts about how to approach the problem. I am sorry that you invested your time into answering this question. Perhaps, in the future, you will be a little choosier about which questions you choose to answer. – Xander Henderson Jul 13 '20 at 23:49
• @Xander, we do sometimes keep low quality questions that provoke high quality answers. I can't see question or answer so I can't say whether that applies here. – Gerry Myerson Jul 14 '20 at 2:36
• @GerryMyerson What do you mean "we"? I was expressing my opinion (note the large number of first person singular pronouns in the text), and hoping to convince others to follow my lead. You appear to have a contrary opinion. Wuderbar. But please don't phrase your opinion in such a way that you give the appearance of speaking for the rest of the community. Again, what do you mean "we"? – Xander Henderson Jul 14 '20 at 3:42
• BTW you linked to your answer rather than to the question. The wording suggests that you probably wanted to link to the question. – Martin Sleziak Jul 14 '20 at 4:43
• @MartinSleziak I just requested to undelete this because I have invested time to think about the solution and I solved this using pigeon hole principle. It's an undeniable fact that this a very good and seemingly unexpected application of pigeon hole principle. I think it should be undeleted. I have nothing more to say. – KKK Jul 14 '20 at 5:02
• I thought I made it clear, Xander, that I was not expressing any opinion on the merits or otherwise of the deleted question or of Shubhrajit's answer. On the other matter you raise, I think it is a fact, and not an opinion, that occasionally we – the m.se community – find an answer of such high quality that we choose to keep it on site despite the failings of the question that prompted it. – Gerry Myerson Jul 14 '20 at 6:00
• @GerryMyerson My understanding is that the community usually have huge argument about what to do with low quality question with great answers. In some heated case the mods even had to lock the question to stop the delete/un-delete war. – Arctic Char Jul 14 '20 at 17:06
• @Arc OK, but I see nothing in what you've written that contradicts what I wrote. – Gerry Myerson Jul 14 '20 at 23:07

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.)

• I think at least the formulation of the question should be clarified a bit before it is reopened. The first answerer already misunderstood it. – quid Aug 30 '18 at 21:11
• Fair enough. I'll do a slight edit. – Andrés E. Caicedo Aug 30 '18 at 21:16
• 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. – quid Aug 30 '18 at 21:19
• No problem. I gave the edit a second pass. (And thank you.) – Andrés E. Caicedo Aug 30 '18 at 21:22

I nominate https://math.meta.stackexchange.com/q/29570/290189 to be undeleted because this meta question contains moderator's feedback to deal with serial downvotes.

• What information is in that post that is not in the FAQ? Also as it was auto-delered it'd be redeleted. – quid Feb 9 '19 at 12:46
• @quid That post provides real examples of questions being serial downvoted. – GNUSupporter 8964民主女神 地下教會 Feb 9 '19 at 12:48
• How is that useful? – quid Feb 9 '19 at 13:14

Deleted, undeleted, redeleted and merged with another question

I request the undeletion of this question (on denesting $$\sqrt{a-b\sqrt{c}}\,)$$

Reason: I asked this question, and it turned out to be a duplicate. However, this doesn't deserve deletion as this question contains a crucial formula that is a very useful one. It is very useful to me, and it is sad for me to see that the community is not able to access it anymore. Please undelete this question.

• The answers there are dupes of the answers in the linked dupe thread (and many others - this is a FAQ). I see no reason to further such rampant duplication. – Bill Dubuque Mar 1 '19 at 1:03
• @BillDubuque there is a useful formula. Perhaps if you can transfer the answer to the other question?? I find it really useful. – Max0815 Mar 1 '19 at 1:04
• That well-known formula is already in Frank's answer in the dupe (and many, many other answers here). Moreover, he derives if instead of pulling it out of a hat as in the answer in your thread. – Bill Dubuque Mar 1 '19 at 1:06
• @BillDubuque how is it derived? even if so, the other answer on my question has a basic method that is not included in the other question. – Max0815 Mar 1 '19 at 1:08
• @BillDubuque oh, right. – Max0815 Mar 1 '19 at 1:11
• I don't understand why this question was deleted. It seems to me that the only reason is that it is a duplicate. I do not believe that this is a reason to delete duplicated (and this was discussed recently here). – user1729 Mar 7 '19 at 13:10

Undeleted, deleted, undeleted, reopened

Please undelete On a colon ideal in the polynomial ring $\mathbb R[x,y]$ because this question has got a score of 2 after OP included his/her own thoughts on the problem. This algebraic geometry question might add value to the main site.

• Selfdeleted without answer. No need to undelete. – quid Feb 25 '19 at 9:16

Undeleted, redeleted, re-undeleted, redeleted, undeleted

Please consider undeleting the question: The asymptotic behavior of $$n\ln n -n$$

• Well, I'd consider something in the spirit of the comment as the best answer there. Anyway given the complete lack of context it's hard to know which type of answer would be useful, whence the voluminous list. Also all standard likely on the site in similar form tens if not hundreds of times. At least one answerer made the effort to link it to related posts. – quid Jun 6 '19 at 22:37
• 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. – user9464 Jun 17 '19 at 22:01
• Probably I should have refrained of posting an answer there - however at the time when I posted there were some answers already and they seemed (to me) more complicated than needed. I have also included links to some other questions - you can see that similar questions are on the site (and they have similar answers). I will also say that when posting the answer I was fully aware that the question is likely to be closed/deleted. – Martin Sleziak Jun 18 '19 at 17:35
• @MartinSleziak: I believe "closing" is enough for this particular post. I strongly disagree with the deletion considering the high qualities of answers. Such good contents will be useful for future readers (this is closed post is not some stupid trivial textbook exercise) and should be preserved on the site. – user9464 Jun 28 '19 at 12:22
• @Jack Well, several discussions here on meta suggest that when deciding about closing (and probably also deleting), most users take into account mainly quality of the question (and do not look at answers). Since you have mentioned that you care about preserving context, I should specifically point out that my answer contains some links to other posts which use Stol-Cesaro. Will Jagy reposted his answer in another thread. (For obvious reasons, I might be a bit biased in this particular case.) – Martin Sleziak Jul 6 '19 at 17:55

Undeleted, deleted, undeleted, reopened, closed as duplicate (mod)

Please consider undeleting this post: 2011 IMC Section A Problem 3

This is not an ongoing contest problem. The answer is known online. @Aqua's answer (with 14 net upvotes) is a useful one.

• Poorly explained answer. Had downvoted it back then. – quid Jul 6 '19 at 19:53
• That was a really bad excuse for deletion. – user9464 Jul 6 '19 at 21:09
• Since I did not delete it, I don't need any excuse (and I doubt the delete-voters where aware of my voting back then). Please do not write comments that might suggest otherwise as not everybody can check it easily. – quid Jul 6 '19 at 22:20

Undeleted, deleted, undeleted, deleted, undeleted, reopened

Please consider casting the final undelete vote and reopening this post:
Evaluate $$1+2-3-4+5+6-7-8+\cdots+50.$$

This question is well written and with effort. It has very well written answers, one of which gives a generalization of the problem.

Reopened

I propose reopening Has Gödel’s second incompleteness theorem been formalized?

The question simply asks whether there is a computer-verified version of the proof of the theorem. This strikes me as a perfectly reasonable mathematical question, and I can't see why anyone would vote to close it, much less delete it (there are currently two votes to delete).

Full disclosure: I posted an answer (the only answer) to the question, which OP has accepted. The answer attracted a downvote – I'm guessing that was done to make it easier to close and delete the question, since I can't see what objection anyone could have to the answer.

REOPENED, Closed

I request to reopen Why does $f(z) = z^n$ have no antiderivative only for $n=-1$? It was closed as a duplicate of Antiderivative 1/z on C.

I disagree that it is a duplicate. The first question was a soft question and the second was a hard question. OP wasn't literally asking for a proof that $$1/z$$ doesn't have an antiderivative. He was asking what makes $$n=-1$$ "special". This is a different question. One question is soft and the other is hard.

I'm studying Poisson Processes. If i have two overlapping time intervals of the same Poisson Process, what are the effects on PMF of the numbers of arrivals in these two intervals ?

This question, quoted above, was closed for lack of details or clarity. Is there anything besides what is in every textbook that is needed in order to understand it? Is there some ambiguity in the question that I cannot see?

• I imagine that the "details" requested are not details of the mathematics but details about the person who posted the question, as to what the user does or doesn't understand about the topic. The less one knows about the user (and given a question stated as in this case, we know virtually nothing about the user), the harder it is to write an answer the user will find useful. Michael, that's how it's been going here for years now, surely you've noticed? – Gerry Myerson Sep 26 '20 at 0:59

Deleted, undeleted, deleted

May I request to Undelete and Reopen (or at least undelete) this question Prove $$\frac{ab}{a^5 + b^5 + ab} + \frac{bc}{b^5 + c^5+ bc} + \frac{ca}{c^5 + a^5 + ca} \leq 1$$ when $$abc=1$$, $$a,b,c>0$$ answered by me? The question is well written and it's a very tricky inequality.

• Let me invite you again to read the instruction at the top of this thread. (1) A request should be posted as an answer below (one request per answer) – Arctic Char Jul 23 '20 at 16:56
• (2) Do not only post a request, like "request reopening of link" – Arctic Char Jul 23 '20 at 16:57
• I have edited it. Sorry. – KKK Jul 23 '20 at 17:02
• I requested (by flagging the moderators) that both of your inequality threads be merged with their duplicates). I hope that they oblige, although my merging requests have been turned down a few times, so I am not too optimistic. – Batominovski Jul 23 '20 at 17:04
• I see @Batominovski – KKK Jul 23 '20 at 17:07
• I didn't really understand why it was deleted? – KKK Jul 23 '20 at 17:09
• It is likely that they will refuse to merge at least one thread. The questions are not exactly the same in this deleted thread as in its duplicate. In the deleted thread, $abc\geq 1$ is the constraint. In the duplicate, $abc=1$ is the constraint. (However, this difference doesn't affect the proof at all.) – Batominovski Jul 23 '20 at 17:10
• @Batominovski yeah. – KKK Jul 23 '20 at 17:12
• You are expected to make a case for undeleting and/or reopening a question, Shubhrajit, not just a request. – Gerry Myerson Jul 23 '20 at 22:06
• @GerryMyerson what do you mean? – KKK Jul 24 '20 at 3:11
• I mean, Shubhrajit, that you are supposed to make some attempt to try to convince us that it would be a good idea to undelete/reopen the question. – Gerry Myerson Jul 24 '20 at 3:18
• If the question does get reopened, shouldn't it be closed as a duplicate of the question Martin noted in a comment? – Gerry Myerson Oct 11 '20 at 21:27
• I voted to delete this question as it is simply the statement of the problem, with no effort shown by the asker. – user1729 Oct 12 '20 at 8:57

Prove $\int g(x) f(g(x)) g'(x) \,dx = \int uf(u)\, du$

This question has been clarified since it was first posted. This is about indefinite, rather than definite integrals. If it could only admit a formal answer rather than a logical answer, maybe it wouldn't be worth much, but that is not the case, as can be seen in the answer that I posted.

• And therefore, you are proposing ... what? – Gerry Myerson Nov 8 '20 at 5:35
• What is a "logical answer"? – Andrés E. Caicedo Nov 8 '20 at 19:41
• @AndrésE.Caicedo : I think you will see what I mean if you contrast what I wrote with the other answers. – Michael Hardy Nov 9 '20 at 5:06
• I read the whole thing before asking. – Andrés E. Caicedo Nov 9 '20 at 13:27
• @AndrésE.Caicedo : Did you look at the way the question was phrased before editing and at the answers other than mine as they first appeared? It said: $$\text{begin quote}$$ I am trying to prove the formula $$\int g(x)f(g(x))g'(x)\,dx=\int uf(u)\,du.$$ $$\text{end quote}$$ And two posted answers applied the chain rule in a formal way, and by "formal" I mean it fit the form without being fussy about whether it's logically rigorous, as in first-year calculus textbooks. My own answer began by saying that if these are indefinite integrals, then the question is$\,\ldots\qquad$ – Michael Hardy Nov 9 '20 at 20:09
• $\ldots\,$meaningless unless $x$ and $u$ are somehow related, and then explained how they would need to be related in order that the identity be true, and proved it. $\qquad$ – Michael Hardy Nov 9 '20 at 20:10
• @AndrésE.Caicedo : $\qquad \uparrow \qquad$ So I mean "formal" in the sense in which the equality $$\int_{-\infty}^{+\infty} \delta'(x)f(x)\,dx = -f'(0)$$is formal when done the way Paul Dirac originally did it, as opposed to the way people like Laurent Schwarz did it later. $\qquad$ – Michael Hardy Nov 9 '20 at 20:12
• I still don't see what you are proposing, Michael. – Gerry Myerson Nov 28 '20 at 21:30

I think we need to open the following Mike Lyons's answer: The smallest value of $$x^2 + 5y^2 + 8z^2$$ such that $$yz+zx+xy=-1$$

I think it's a beautiful and right answer. We need to redact it only.

It was my mistake to delete this answer.

• Note that the question has since been deleted. – Gerry Myerson Oct 9 '18 at 22:27

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.

• 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]. – Did Sep 8 '18 at 22:17
• "By the way, the first comment of Lord Shark the Unknown it's nothing" Pfff... – Did Sep 8 '18 at 22:44
• And now there's a rollback war. – Gerry Myerson Oct 1 '18 at 12:35
• 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!!! – user1729 Oct 12 '18 at 17:11
• 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! – Gerry Myerson Oct 15 '18 at 22:44
• 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. – user296602 Nov 27 '18 at 18:28

Undeleted, closed, re-deleted (not by question-asker this time)

Please reopen https://math.stackexchange.com/q/3129981/290189 because the question asker has self-deleted his/her own post after getting an answer. The communnity has not got enough time to judge its value.

I would like to see this question undeleted and mark as duplicate but keep it alive on the network.

Also, I object to the deletion since although the questions are looking for the same thing, I must mention that they are not word by word duplicates and the context also seems a bit different. Also, the answers are not duplicates (except one which coincidentally was answered by the respective OPs of both questions).

• This question was deleted by a moderator, which means that only a moderator can undelete it. As such, there is pretty much nothing that anyone here can do for you. – Xander Henderson Apr 5 '19 at 17:50
• @XanderHenderson I posted this on meta. Someone asked me to post here (just to be shot with 3 odd downvotes here ) – tatan Apr 5 '19 at 18:54
• Votes on meta do not mean the same thing that they mean on the main site. A downvote means "I do not agree with this statement." I would interpret the downvotes here as an indication that the community does not want to reopen / undelete your question. – Xander Henderson Apr 5 '19 at 20:50
• @Aloizio Macedo can you please give some reasons on why you single-handedly deleted the question? (as it stands it looks like an abuse of power, but maybe there'a reason that I'm missing) – Zacky Jul 22 '19 at 9:16