The sites in this category are related to competitions and mathematical Olympiads, but must also contain content of interest to those not involved in the competition.

This category is for solutions, hints and online versions of famous math problems.

A flexagon is a hexagon, which you can make from a strip of triangles. The objective is to open the flexagon in the middle and have a previously hidden face appear. Arthur Stone, an English graduate student, was in the practice of doodling with the strips of paper that he cut from around the edges of his notebook paper. American paper was too large for his English binder. One of the constructions arising from this happy misfortune attracted his attention in particular. A committee of graduate students formed to solve the mystery of the "flexible hexagon", or, as it soon became known, the "flexagon." The members of this group-- Richard P. Feynman, Bryant Tuckerman, John W. Tukey, and Arthur H. Stone, had laid the groundwork for all consequent study, through developing their yet unpublished theory, by the early 1940's. When the group disbanded, the flexagon was left, nearly forgotten, for ten years. Then, toward the beginning of the fifties, it received slight publicity with several very brief articles in mathematics magazines.

This category contains educational web sites containing mathematical problems, games, puzzles, or quizzes. Sites whose emphasis is on mathematical education are welcome to submit in this category.

A Magic Square of order n is an arrangement of the numbers from 1 to n^2 (n-squared) in an n by n matrix. The sum of any row, any column, or any main diagonal must be the same. The smallest non-trivial case is of order 3.

The same idea can be extended to other shapes such as stars, cubes, circles, and so on. These are called Magic objects.

Some say that numbers aren't as important as actual functions, but we say they are! :-) For anyone who has wondered why 13 is unlucky, why you can't eat pi, or why 1 is the multiplicative identity, this is the category you've been searching for since grade school. Whatever intellectual curiosity has been nagging at you since you first wrote the number 5, you will be likely to find an answer to your question here. And if not, submit your own! Also: Definitions of important constants, formulas to compute them and formulas that use them.

Mathematical recreations involving tessellations or tiling.