English

Pattern avoidance and the fundamental bijection

Combinatorics 2024-07-10 v1

Abstract

The fundamental bijection is a bijection θ:SnSn\theta:\mathcal{S}_n\to\mathcal{S}_n in which one uses the standard cycle form of one permutation to obtain another permutation in one-line form. In this paper, we enumerate the set of permutations πSn\pi \in \mathcal{S}_n that avoids a pattern σS3\sigma \in \mathcal{S}_3, whose image θ(π)\theta(\pi) also avoids σ\sigma. We additionally consider what happens under repeated iterations of θ\theta; in particular, we enumerate permutations πSn\pi \in \mathcal{S}_n that have the property that π\pi and its first kk iterations under θ\theta all avoid a pattern σ\sigma. Finally, we consider permutations with the property that π=θ2(π)\pi=\theta^2(\pi) that avoid a given pattern σ\sigma, and end the paper with some directions for future study.

Keywords

Cite

@article{arxiv.2407.06338,
  title  = {Pattern avoidance and the fundamental bijection},
  author = {Kassie Archer and Robert P. Laudone},
  journal= {arXiv preprint arXiv:2407.06338},
  year   = {2024}
}

Comments

21 pages

R2 v1 2026-06-28T17:33:30.922Z