MathDB
Function with factorial

Source: Shortlist BMO 2018, N2; Albania TST problem 1; Macedonia TST problem 4

May 2, 2019
functionfactorialnumber theory

Problem Statement

Find all functions f:NNf:\mathbb{N}\rightarrow\mathbb{N} such that n!+f(m)!f(n)!+f(m!)n!+f(m)!|f(n)!+f(m!) for all m,nNm,n\in\mathbb{N} Proposed by Valmir Krasniqi and Dorlir Ahmeti, Albania