one of a^n+1, a^{n+1}+1 , ... , a^{2n-2}+1 does not have a common divisor
Source: Rioplatense Olympiad 2012 level 3 P5
September 4, 2018
number theorydivisor
Problem Statement
Let and be integers . Prove that one of the numbers does not share any odd divisor greater than with any of the other numbers.