Cannonball problem

English

Etymology

It can be visualized as the problem of taking a square arrangement of cannonballs on the ground and building a square pyramid out of them.

Proper noun

1. Template:Lb The challenge of proving that the only solution of the Diophantine equation :$\sum _{n=1}^N{n}^2=M^2$ with N > 1 is when N = 24 and M = 70.