Problem

Source: Norwegian Mathematical Olympiad 2000 - Abel Competition p1b

Tags: Perfect Square, number theory



Determine if there is an infinite sequence $a_1,a_2,a_3,...,a_n$ of positive integers such that for all $n\ge 1$ the sum $a_1^2+a_2^2+a_3^2+...^2+a_n^2$ is a perfect square