Think of a number, square it and subtract your starting number. Is there something special about the number you are left with?

This week would have been the 100th birthday of Martin Gardner, who is deservedly credited with turning on several generations of people worldwide to the pleasures of maths! To mark the occasion here are some favourite puzzles that, apart from being fun, also lead to some serious maths.

After 5,000 years, the game of Nine Men's Morris has succumbed to the power of modern computing, plus other recent mathematical discoveries in the world of games.