English

Completing the enumeration of inversion sequences avoiding triples of relations

Combinatorics 2025-12-29 v1

Abstract

An inversion sequence of length nn is an integer sequence (a1,,an)(a_1, \ldots, a_n) such that 0ai<i0 \le a_i < i for all ii. The study of pattern-avoiding inversion sequences was initiated in 2015 by Mansour and Shattuck and in 2016 by Corteel, Martinez, Savage and Weselcouch. Martinez and Savage later defined a new type of pattern, a triple of binary relations, of which there are currently 14 uncounted avoidance classes. We complete the enumeration for all of these classes using generating tree methods "growing on the left" and "growing on the right". For many of these classes we are able to find algebraic generating functions. We also discuss the asymptotic behaviour of the counting sequences.

Keywords

Cite

@article{arxiv.2512.21943,
  title  = {Completing the enumeration of inversion sequences avoiding triples of relations},
  author = {Nathan Britt and Nicholas Beaton},
  journal= {arXiv preprint arXiv:2512.21943},
  year   = {2025}
}

Comments

24 pages

R2 v1 2026-07-01T08:41:22.876Z