Ascent sequences avoiding a triple of 3-letter patterns and Fibonacci numbers
David Callan, Toufik Mansour · The Art of Discrete and Applied Mathematics · 2024
We consider triples τ of 3-letter patterns for which ascent sequences that avoid τ are counted by Fibonacci-related numbers. Several cases are equivalent to avoiding a pair of 3-letter patterns and have already been treated using generating functions. Here we give direct proofs of all our results. We also consider avoiders for some quadruples of 3-letter patterns.