2012 BMO Problems/Problem 4
==2012 BMO Problems/Problem 4
Problem
Find all functions (where is the set of positive integers) such that for all positive integers and such that divides for all distinct positive integers , .
Solution
This is the same problem as the 2012 USAMO Problem 4. See https://artofproblemsolving.com/wiki/index.php/2012_USAMO_Problems/Problem_4.