What is on Your Mind?

Some might already have guessed it: i am as much mathematically challenged as i am mathematically inclined.(*) This old (and largely unresponded) love of mine fell mostly short in the daily work as a programmer but was ignored completely in my work as a systems administrator.

To my utter delight i found a web site which piques my mathematical interest as much as it appeals to my programming skills, so i thought you might want to try yourself how well you fare:

Project Euler

poses problems, solvable by either brute computational force (if you are able to implement the necessary algorithms) or by mathematical reasoning, sometimes you even need both to succeed. There is nothing to win save for the satisfaction a solved problem will generate. There is nothing to lose either - sans some hours of your time spent with thinking.

I hope you enjoy but, please, DO NOT POST solutions. Others might want to solve the problems themselves.

bakunin
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(*) that means about: i have a vague picture of what, for instance, a Dedekind Cut is, but i still can do integer addition without a calculator

I use to do these to kill time. It's probably how I learned the Sieve of Eratosthenes.

I've done a lot of them for fun. I stopped at about 230 - the highest number then was around 310. The list is now 450+.

You need to know some number theory and have a compiler or other access to a bignum library - perl, numpy, C, fortran. I used GNU C with GMP on Cygwin.

I second the idea: do not post solutions elsewhere. You are not helping anyone by doing that.