Project Euler is a series of challenging mathematical/computer programming problems. Please see the site and rules before posting.

(copied from Project Euler site)

Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.

The motivation for starting Project Euler, and its continuation, is to provide a platform for the inquiring mind to delve into unfamiliar areas and learn new concepts in a fun and recreational context.

Before asking anything about problems in Project Euler, read this question in the meta and this thread in Project Euler forum. Most important things are:

Project Euler

*does not*want their participants asking elsewhere, they want them to experiment, solve easier sub-problems, etc.They

*do not*want answers, or parts of answers, publicly visible.