MathDB
n(n+3) a perfect square => 3 not a multiple of 3

Source: Greece JBMO TST 2007 p2

June 17, 2019
number theoryPerfect Squaremultiple

Problem Statement

Let nn be a positive integer such that n(n+3)n(n+3) is a perfect square of an integer, prove that nn is not a multiple of 33.