IMO 2016 Shortlist N6
Denote by N the set of all positive integers. Find all functions f : N → N such that for all positive integers m and n, ...
Category: Number Theory
Problem
Denote by N the set of all positive integers. Find all functions f : N → N such that for all positive integers m and n, the integer f(m) + f(n) − mn is nonzero and divides mf(m) + nf(n). 10 IMO 2016 Hong Kong