MathDB
11|a^n+b^n -> 11|a,11|b for all a,b, find n

Source: VJIMC 1999 1.2

August 1, 2021
number theory

Problem Statement

Find all natural numbers n1n\ge1 such that the implication (11an+bn)    (11a11b)(11\mid a^n+b^n)\implies(11\mid a\wedge11\mid b)holds for any two natural numbers aa and bb.