On (shape-)Wilf-equivalence for words

Abstract

Stankova and West showed that for any non-negative integer $s$ and any permutation $\gamma$ of $\{4,5,\dots ,s+3\}$ there are as many permutations that avoid $231\gamma$ as there are that avoid $312\gamma$. We extend this result to the setting of words.

AmS-LaTeX, 13 pages; minor improvements