Can we ask Project Euler questions here?

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    $\begingroup$ It is against the rules of Project Euler. $\endgroup$ – hunter Jun 18 '20 at 21:07
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    $\begingroup$ @hunter: That seems to be particularly cut and dried. Citation needed, perhaps? The Project Euler copyright page suggests to me that by the terms of its CC BY-NC-SA 4.0 license, sharing the problems is permitted with attribution and for non-commercial purposes. Did you mean that StackExchange is a commercial enterprise and posting the problems (which involve programming as well as mathematics) would be against that rule? $\endgroup$ – hardmath Jun 18 '20 at 22:02
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    $\begingroup$ Some older related discussions: Re: Project Euler questions and Project Euler, again. $\endgroup$ – Martin Sleziak Jun 18 '20 at 22:24
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    $\begingroup$ There is a project-euler tag and (apparently) 160 questions that have it. $\endgroup$ – Peter Phipps Jun 18 '20 at 22:32
  • $\begingroup$ With the best will in the world, I don't see how the maths.SE community can be expected to be on the alert for (at time of writing) 720 Project Euler problems. $\endgroup$ – Peter Phipps Jun 19 '20 at 9:21
  • $\begingroup$ @hardmath I am surprised to say their "about" page seems to have changed. Now I'm not sure, although the copy of the "about" page in the comments on the answer contains the language from before. $\endgroup$ – hunter Jun 19 '20 at 17:46
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    $\begingroup$ @hunter please see the letter from the P.E. guy in my answer; it is also in some of the linked Meta posts. $\endgroup$ – Will Jagy Jun 19 '20 at 18:18
  • $\begingroup$ @PeterPhipps if I see them I post a letter I got from P.E. as an answer; I also put it here, most of the high reputation users here have seen it. People actually argue with me about what the writer "hk" means, but there it is. $\endgroup$ – Will Jagy Jun 19 '20 at 18:24

Here is the stuff I put at such questions, when I notice them. The important part is a letter (email) from one of the P.E. people; two kids had posted P.E. problems on MO the same day they were asked.



discussion on MO:



discussion at Project Euler's own forum:



email letter from "hk", Novemeber 2011

Hi Will,

let me introduce myself to you. I'm hk at Project Euler. The philosophy of Colin Hughes, the founder of Project Euler was the philosophy of inductive self learning. Just Googling on the subject will reveal you quite a lot about this educational subject. (The top item on my version of Google was this one: http://mate.calpoly.edu/media/files/Review_inductive_learning.pdf)

My personal view on this matter is: if you lack the attitude, when faced with a new problem, to break it down into smaller parts or to investigate smaller cases you will never never become a successful scientist or academically schooled person. The problem in question that raised attention to Project Euler is particularly fit for scaling down and discover some useful facts.

I think we are facing a cultural clash here: The rationalisations shown to us by e.g. rbharvs are from the level: I have to be told how to do things. I'm afraid that has to do with a failing educational system that shows students rules and formulas without giving them enough room to experiment before formalising knowledge.

To do some work that is new to you, be it research mathematics or toying around with problems for which all underlying maths is known, you will need to doodle around with the problem or parts of it. How else can one do essentially new work? Top down teaching that doesn't help their students to develop this kind of ability produces people that start shouting: tell me how to do it and I will try to copy it. Some people that are badly educated in the way I sketched are just using Project Euler to develop those skills. I hope that they will benefit from that in their professional life. Some have even indicated that it was Project Euler that ultimately made them decide to choose mathematics for their academic study despite the poor level of the mathematical education in their country.

The people that posed the questions at Math Overflow, in my opinion have shown to lack the mental attitude to do the necessary doodling around. (Take for instance the fact that one of them copied the radius 10^10. Some experimenting would have shown them that ______).

Well, you can consider this private communication as lunch talk if it doesn't interest you, but I hope I gave you some information about the philosophy of Project Euler. Feel free to paraphrase it to your wish when communicating with your colleagues at Math Overflow. If you like to know more feel free to email me.

Thanks again for the effort you have invested in the case.





I vote: No, do not ask questions form Project Euler on Math.se. Instead, follow the rules of Project Euler.

But Math.se will not stop you from asking. Of course, Math.se will also not stop our users from closing such questions.

As noted in a comment, the Project Euler copyright license requires that you attribute the problem to them when you post it here. But the only enforcement of that would be if Project Euler notices a non-attributed post and requests Math.se to take it down.

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    $\begingroup$ I've had a look on the website, and so far as I can see they give no general "rules". However, it may be against the spirit of Project Euler to ask here. $\endgroup$ – user1729 Jun 19 '20 at 14:36
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    $\begingroup$ @user1729 they say explicitly that it is not okay to publish solutions. It's framed in the context of publishing ones own solution, but by extension and due to the underlying reasoning it clearly applies to soliciting publication of solutions. Of course this is not in a legal sense, but it is directly against the expressed wishes. They are more open to spreading the problems, but that's not what they site here is about. If it is aksed here the intent is to get a solution published. $\endgroup$ – quid Jun 19 '20 at 15:21
  • $\begingroup$ @quid Ok, but then I have two question: where did you find this? (Seriously - I had a long look and was even googling "rules site:projecteuler.net"!) Secondly, asking for hints isn't covered by this rule, right? $\endgroup$ – user1729 Jun 19 '20 at 15:33
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    $\begingroup$ @user1729 it's even in the "about" projecteuler.info/about ; penultimate point. Also projecteuler.chat/viewtopic.php?f=5&t=3078 It's very, very clear that they don't want this. Re "Hints" I don't know why you keep pushing this. PE even has ther own board for users that want to engage in discussions. Maybe one can construe asking for a hint as researching the problem, but frankly I find that a stretch. $\endgroup$ – quid Jun 19 '20 at 17:42
  • $\begingroup$ @quid it appears to have been removed from the main site at projecteuler.net, although i don't see why. $\endgroup$ – hunter Jun 19 '20 at 17:46
  • $\begingroup$ @hunter thanks; I did not realize that I was on a static back-up site as I arrived there via a search. $\endgroup$ – quid Jun 19 '20 at 17:50
  • $\begingroup$ @quid I am not "pushing this"; neither of my comments have any agenda other than seeking clarity. (Incidentally, I don't see why PE having their own board means people should not ask elsewhere about it. That strikes me as being a weird policy for us to have.) And yes, as per hunter's comment, in the current version of their website it is not clear that they do not want this. Possibly their policy has changed? $\endgroup$ – user1729 Jun 19 '20 at 18:08
  • $\begingroup$ @user1729, please see the letter in my answer, if you have not seen it already in the linked Meta posts. $\endgroup$ – Will Jagy Jun 19 '20 at 18:19
  • $\begingroup$ @user1729 Questions for hints are always borderline, anyway. Most of the questions coming from such things are anyway poor. I am pretty sure that they still do not want to have solutions floating around. Etc. Sorry if I might seem impatient, but I don't see why "don't ask about PE here" needs much further qualifcation or discussion. Maybe there can be some exceptional circumstance but I don't see the need to detail this. $\endgroup$ – quid Jun 19 '20 at 18:48

We also have a contest policy. It states that questions from on-going contests are not allowed, but questions past their due date are ok. Admittedly that policy was developed with national/regional/whatnot pure math competitions in mind. It is not entirely clear to me, where Project Euler fits in given that there tasks also involve a non-trivial amount of coding. But the sentiment of that policy is to protect the integrity of such contests to the best of our ability. Many users here have been involved in organizing contests, and want it this way.


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