Finite and infinite arithmetic progressions in sumsets

Abstract

We prove that if $A$ is a subset of at least $cn^{1/2}$ elements of $\{1, \dots, n\}$, where $c$ is a sufficiently large constant, then the collection of subset sums of $A$ contains an arithmetic progression of length $n$. As an application, we confirm a long standing conjecture of Erdős and Folkman on complete sequences.