Determine f(30)
Source: IMO Longlist 1989, Problem 96
September 18, 2008
algebra unsolvedalgebra
Problem Statement
Let be such that
(i) is strictly increasing;
(ii) f(mn) \equal{} f(m)f(n) \forall m, n \in \mathbb{N}; and
(iii) if and m^n \equal{} n^m, then f(m) \equal{} n or f(n) \equal{} m.
Determine