MathDB
sequences cover Z

Source: VJIMC 2009 1.4

June 12, 2021
Sequences

Problem Statement

Let (an)n=1(a_n)_{n=1}^\infty be a sequence of real numbers. We say that the sequence (an)n=1(a_n)_{n=1}^\infty covers the set of positive integers if for any positive integer mm there exists a positive integer kk such that n=1ank=m\sum_{n=1}^\infty a_n^k=m.
a) Does there exist a sequence of real positive numbers which covers the set of positive integers? b) Does there exist a sequence of real numbers which covers the set of positive integers?