For positive integer $n$, prove that at least one of the numbers $$A=2n-1 , B=5n-1, C=13n-1$$is not perfect square
Problem
Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2011
Tags: number theory, Perfect Squares
Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2011
Tags: number theory, Perfect Squares
For positive integer $n$, prove that at least one of the numbers $$A=2n-1 , B=5n-1, C=13n-1$$is not perfect square