Problem

Source: Russian Regional Olympiad 2010 11.4

Tags: number theory, Perfect Square



We call a triple of natural numbers $(a, b, c)$ square if they form an arithmetic progression (in exactly this order), the number $b$ is coprime to each of the numbers $a$ and $c$, and the number $abc$ is a perfect square. Prove that for any given a square triple, there is another square triple that has at least one common number with it.