Beschreibung:
<jats:p>A set of words X is called unavoidable on a given alphabet A if every infinite word on A has a factor in X. For k,q≥1, let c(k,q) be the number of conjugacy classes of words of length k on q letters. An unavoidable set of words of length k on q symbols has at least c(k,q) elements. We show that for any k,q≥1, there exists an unavoidable set of words of length k on q symbols having c(k,q) elements.</jats:p>