MathDB

Prove that a necessary and sufficient for the existence of a set

S \subset \{1,2,...,n \}

with the property that the integers 0,1,...,n\minus{}1 all have an odd number of representations in the form x\minus{}y, x,y \in S, is that (2n\minus{}1) has a multiple of the form 2.4^k\minus{}1 L. Lovasz, J. Pelikan

Problem Statement