Strong ordering conjecture for pattern-avoidance classes

From papers

For a permutation τ\tau, let Sn(τ)S_n(\tau) denote the set of permutations in SnS_n avoiding τ\tau. Suppose τ,σS4\tau,\sigma\in S_4. Strong ordering conjecture. If

Sk(τ)<Sk(σ)|S_k(\tau)|<|S_k(\sigma)|

for some kk, then

Sn(τ)<Sn(σ)|S_n(\tau)|<|S_n(\sigma)|

for all nkn\geq k. Equivalently, modulo Wilf-equivalence, permutations can be ordered by relative restrictiveness, with τ<σ\tau<\sigma when Sk(τ)<Sk(σ)|S_k(\tau)|<|S_k(\sigma)| for some kk. This conjecture proposes a global ordering of pattern-avoidance classes by their enumeration sequences; the later table in the paper exhibits counterexamples in S7S_7, so the conjecture is refuted.

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Sources & referencesView supporting material

Primary source

Zvezdelina Stankova-Frenkel and Julian West, “A New Class of Wilf-Equivalent Permutations”, arXiv:math/0103152 (2001).

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