Pattern occurrences in $k$-ary words revisited: a few new and old observations

Abstract

In this paper, we study the pattern occurrence in $k$-ary words. We prove an explicit upper bound on the number of $k$-ary words avoiding any given pattern using a random walk argument. Additionally, we reproduce several already known results and establish a simple connection among pattern occurrences in permutations and $k$-ary words. A simple consequence of this connection is that Wilf-equivalence of two patterns in words implies their Wilf-equivalence in permutations.

Lemma 2.2 is added to close an existing gap in the proof of Theorem 1.1 in an earlier version of the paper