IMC 2013 · Problem 5

Day 120th IMC · Blagoevgrad, Bulgaria

Statement

Does there exist a sequence (an)(a_n) of complex numbers such that for every positive integer pp we have that n=1anp\sum\limits_{n=1}^{\infty} a_n^p converges if and only if pp is not a prime?

Official solution

Hidden so you can work on the problem first.

Proposed by Tomáš Bárta, Charles University, Prague.