Show that there exists a set of infinite positive integers such that the sum of an arbitrary finite subset of these is never a perfect square. What happens if we change the condition from not being a perfect square to not being a perfect power?
Problem
Source: OIFMAT III 2013 day 1 p4 - Chilean Math Forum FMAT Olympiad https://artofproblemsolving.com/community/c2484778_oifmat
Tags: Perfect Squares, Perfect Square, Perfect power, number theory