Erdős: Mathematical problems

Previous discussion from the last time it was posted: https://news.ycombinator.com/item?id=8313702.

We have since gotten new problems and a few new features (such as a newsletter to announce new contests).

this looks more organized and varied than project Euler.

the most recent puzzle is a clone of a game called Hackenbrush :-) http://www-math.mit.edu/~rstan/transparencies/games.pdf