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Proposed Release Schedule for New Problems

All dates/times are showing for Europe/London timezone.

  • Problem 559: Saturday, 7th May 2016, 04:00 pm
  • Problem 560: Saturday, 14th May 2016, 07:00 pm

Recent News

23 December 2015: New Forum

Some of you will be aware that the alternative forum which many of you use regularly went offline a couple of days ago without notice. We would like to apologise for this, but it was to carry out some essential maintenance. However, you will be pleased to know that the forum is available again at a new web address:

It is hoped that everything has transferred across without any problems, but, as always, if you notice anything unusual then please let us know at the new forum.

9 August 2015: Project Euler Help

In light of the last news item in which I appealed to the Project Euler community to assist in identifying the method of the recent hack I have been completely overwhelmed in two respects: literally the number of emails received and by the generosity of your time, expertise, and willingness to help. Thank you!

I have already responded to some emails and thanks to their insights a few bugs have now been exterminated.

One common query has been whether or not the scripts for the website can be made publicly available. This is something I am reluctant to do, but in due time I will be taking up some very kind offers to help by forming a small team of developers to view the scripts privately.

Be assured that I have read every email received, but please do not be offended if I am unable to reply to everyone. If you have made an offer to help but you are not invited initially I may yet approach you at some point in the future. I truly value every response.

7 August 2015: Project Euler Humble Return

Project Euler is back. However, it has been necessary to restore the database to 28 July 2015 which means that a number of members will have lost a couple of days of progress. It is also with ever greater sadness I report that I have been unable to identify the method of attack used to hack the database. It is quite possible that a similar attack may never happen again or it may happen again and again. If a similar hack occurs then I will be forced to restore the database once more. Clearly this is neither ideal nor can it continue indefinitely. For this reason we are calling on some of you, members of the Project Euler community, with expertise in web security to help identify vulnerabilities in the website. If anyone is able to provide information then not only will it be met with my own personal gratitude but with the appreciation of the rest of the members. Otherwise, if the method of attack is not discovered, and the website continues to be hacked, then the current content (problems and threads) will be permanently converted into a static website; an alternative method of publishing future problems will need to be determined.

So if you have the right skills and you would like to help the community by auditing (hacking) the website then you are invited to do so. However, I would request that any testing is done as a proof-of-concept rather than being destructive in nature. If you do identify a potential vulnerability then I would also ask that you do not publish your findings publicly and contact me privately via email: You have my personal assurance that any constructive actions will receive full amnesty and your communications will be handled in the strictest of confidence.

Be aware that the database could be restored to a previous state at any time so please keep a record of your answers elsewhere. If you feel uncomfortable using this website at the moment then the temporary website (containing the problem set with an answer checker) has been made permanently available at

2 August 2015: Project Euler Hacked

Sadly it seems that a malicious user has discovered a way to modify the contents of the DB. It is currently unclear how this occurred so in the meantime a decision has been made to take Project Euler offline and replace it with a temporary website. This will ensure that the problems, which are the primary reason Project Euler exists, remain accessible. During this time you will be pleased to learn that it is possible to check answers.

Further updates will be made through this news feed.

22 June 2015: Summer break

Problem #522: (Sunday, 28th June 2015, 04:00 am servertime) will be the last problem before the summer break.
We will be back Sunday, September 6th, 2015.