MathDB
Nice integer FE

Source: 2020 Caucasus Mathematical Olympiad Seniors Problem 4

March 16, 2020
functional equationalgebranumber theory

Problem Statement

Find all functions f:NNf : \mathbb{N}\rightarrow{\mathbb{N}} such that for all positive integers mm and nn the number f(m)+nmf(m)+n-m is divisible by f(n)f(n).