There seems to be something quite dissatisfying about questions that simply copy/paste questions from Project Euler. For example:

Find the sum of all the multiples of 3 or 5 below 1000

From the Project Euler website:

I solved it by using a search engine, does that matter?

Making use of the internet to research a problem is to be encouraged as there could be hidden treasures of mathematics to be discovered beneath the surface of many of these problems. However, there is a fine line between researching ideas and using the answer you found on another website. If you photocopy a crossword solution then what have you achieved?

Secondly, once a question is answered a forum is presented which usually contains a long list of methods for solving the question in question.

So my feeling is that they do not want (more) answers to their problems posted online.

Any thoughts on how to best deal with this?

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    $\begingroup$ Can we honestly be expected to check every question to see whether it comes from Project Euler? There will always be kids who want to take the easy way out instead of using their brains. If it is not Project Euler, it will be something else. $\endgroup$ Nov 7, 2010 at 22:45
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    $\begingroup$ If they have to ask here for complete solutions anyway, they're missing the damned point of the project. $\endgroup$ Nov 7, 2010 at 23:40
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    $\begingroup$ @J. M.: no kidding. Cheating on Project Euler is the very definition of cheating oneself... $\endgroup$ Nov 8, 2010 at 0:35
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    $\begingroup$ The responsibility lies on the person asking. $\endgroup$
    – anon
    Nov 8, 2010 at 10:24
  • $\begingroup$ @Willie Wong: What if the mathematics behind an existing math.SE question becomes the central plank in a future Project Euler question? Or do you see that as being Project Euler's responsibility? (This comment should be attached to your answer but I don't want to spoil your voting mechanism.) $\endgroup$ Dec 9, 2011 at 20:56
  • $\begingroup$ @PeterPhipps: One thing that I don't see directly mentioned here is the "why". Why would kids "cheat themselves" on Project Euler? I suspect that this has to do with the fact that PE gives special recognition to the fastest solvers of a given new question, so some people are motivated by wanting to get an answer as fast as possible. The only way I can justify (to myself) closing questions of these sorts is that they spoil a competition/exam/course of study by helping certain fraction of the participants cheat. In the present context the argument becomes a lot weaker if the offending question.. $\endgroup$ Dec 10, 2011 at 12:39
  • $\begingroup$ ..was asked before (or long after) the Project Euler problem was made available. Oh, and thanks for not commenting on the answer itself. I appreciate that. $\endgroup$ Dec 10, 2011 at 12:40

3 Answers 3


There was some debate on this on MO, when two people asked for contributions to P.E. question number 360, disguising the question a little and, quite deliberately, not giving attribution. People were uncertain, so I contacted P.E., a post at: http://projecteuler.chat/viewtopic.php?f=5&t=2707

As you can see, the language of the moderator/admin is quite strong. I also got email from the fellow, he was absolutely disgusted.

So, MSE must decide what MSE wants to do. However, Project Euler (1) does not want their participants asking elsewhere, they want them to experiment, solve easier sub-problems, etc. (2) they do not want answers, or parts of answers, publicly visible.

I brought this up because of Integer coordinate set of points that is a member of sphere surface

which is part of http://projecteuler.net/problem=360 whatever the OP intended.

  • $\begingroup$ The first link above is broken. The same post can now be found here: projecteuler.chat/viewtopic.php?f=5&t=2707 $\endgroup$
    – Winther
    Jan 9, 2017 at 5:14
  • $\begingroup$ @Winther thank you. I edited this one and another post on the same topic, here on meta. I also fixed the ordinary text file I keep on my home computer, for quick answering on Main; most of that, including the letter from a PE moderator, is at the other question $\endgroup$
    – Will Jagy
    Jan 9, 2017 at 20:22
  • $\begingroup$ The revival link provided by Winther above is now available forever on Wayback Machine. $\endgroup$ Mar 9, 2019 at 21:27

This site and others -- ranging from StackOverflow to Project Euler -- are separate entities and there is no reason to artificially create more correlation between them. What is more internally relevant for math.SE is locating sources for problems or other mathematical material and developing tags that enhance the value of whatever is posted.

A [project-euler] tag would be of interest to users who want to seek or avoid discussion of those problems. (EDIT : this tag exists and has been used for a few questions. I see no reason not to place it on every Project Euler problem that is posted, at least for questions that originate on that site and are not found in other standard sources.)

Tags like [putnam], [AMM], [olympiad] or even [international-olympiad] would help label material from other problem banks with their own special characteristics.

An [unsourced] tag would speed the identification of problems from any unspecified source, including Project Euler. Alternatively, a [sourced] tag would promote the use of sources for all material, including that from Project Euler.

Math is different from programming. What works (or does not work) on StackOverflow, where questions and answers are time-dependent, time-sensitive and contingent on particular software and hardware environments, does not work as well for a math site. Mathematical information is mostly "eternal" and can be cited by reference. It is therefore cumulative and this creates an archival interest in listing of sources as additional data independent from the Q&A.

This reasoning leads not only to tags but to having a structured, searchable SOURCE field, with its own set of tags and forms and check-boxes, as part of the question data. As long as the current SE platform lacks such features, intelligent use of tags can help.


While I still think it is really not any of our business to patrol for Project Euler questions: Given the rather strongly worded response from those responsible for Project Euler (as pointed out in Will Jagy's answer), and previous instances where we have closed/deleted homework/exam questions at the request of professors for assigned those questions, here is a proposal.

Please vote up if you agree that we should do this. And please vote down if you disagree that we should do this.

If one of the Project Euler organisers contact the moderators about questions lifted directly from the Project Euler question list, the moderators should lock/close/delete the question.

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    $\begingroup$ Vote this comment up if you agree with the main proposal and think that the action by the moderators should be to lock the question for a fixed period (7 days, perhaps). $\endgroup$ Dec 9, 2011 at 10:00
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    $\begingroup$ Vote this comment up if you agree with the main proposal and think that the action by the moderators should be to close the question. $\endgroup$ Dec 9, 2011 at 10:00
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    $\begingroup$ Vote this comment up if you agree with the main proposal and think that the action by the moderators should be to delete the question. $\endgroup$ Dec 9, 2011 at 10:00

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