not all sufficiently large integers are clean
Source: 2015 IMO Shortlist C6, Original 2015 IMO #6
July 7, 2016
IMO ShortlistcombinatoricsAdditive combinatorics
Problem Statement
Let be a nonempty set of positive integers. We say that a positive integer is clean if it has a unique representation as a sum of an odd number of distinct elements from . Prove that there exist infinitely many positive integers that are not clean.