This article deals with elementary number theory, in order to find a way to discover connections among the Pythagorean triplets. The main question is whether the smallest or the middle number of the triples has to be even number. There are two connections which are proven by elementary algebraic methods respectively a geometrical remark which turns back probably to Pythagoras or earlier to Babylon. It is a very nice problem for upper secondary school students.

Reviewer:

Ödön Vancsó (Budapest)