A short proof that shuffle squares are 7-avoidable

Abstract

A shuffle square is a word that can be partitioned into two identical words. We obtain a short proof that there exist exponentially many words over the 7 letter alphabet containing no shuffle square as a factor. The method is a generalization of the so-called power series method using ideas of the entropy compression method as developped by Gonçalves et al. [Entropy compression method applied to graph colorings. arXiv:1406.4380].