English

When arrow patterns meet classical patterns

Combinatorics 2026-07-05 v1 Discrete Mathematics

Abstract

Seeking to bridge the structural divide between a permutation's cycle notation and its one-line notation, Berman and Tenner introduced a novel notion of permutation pattern known as the arrow pattern. Recently, Archer and Laudone initiated a systematic study of arrow pattern avoidance, leaving behind three intriguing conjectures. In this paper, we resolve all three conjectures. First, we enumerate all six subclasses of permutations that simultaneously avoid a classical pattern of length 3 and a fixed arrow pattern of length 3, thereby confirming the first two conjectures. Second, we settle the third conjecture (which involves a different arrow pattern) by providing two independent proofs. These proofs rely on a restriction of Biane's bijection to non-nesting involutions and Krattenthaler's bijection from 321-avoiding permutations to Dyck paths, respectively.

Cite

@article{arxiv.2607.04094,
  title  = {When arrow patterns meet classical patterns},
  author = {Shishuo Fu and Zhenghe Yang},
  journal= {arXiv preprint arXiv:2607.04094},
  year   = {2026}
}

Comments

17 pages, 3 figures, 4 tables