Barnabei–Bonetti–Castronuovo–Silimbani's Motzkin enumeration conjecture for alternating involutions

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Let AIm(ρ)\mathcal{AI}_{m}(\rho) and RAIm(ρ)\mathcal{RAI}_{m}(\rho) denote, respectively, alternating and reverse alternating involutions of size mm avoiding the pattern ρ\rho, and let MnM_n be the nn-th Motzkin number,

Mn=∑k=0⌊n/2⌋n!k!(k+1)!(n−2k)!.M_n=\sum_{k=0}^{\lfloor n/2\rfloor}\frac{n!}{k!(k+1)!(n-2k)!}.

Barnabei–Bonetti–Castronuovo–Silimbani's conjecture. For positive integers nn,

∣AI2n(1432)∣=∣AI2n(3214)∣=Mn,|\mathcal{AI}_{2n}(1432)|=|\mathcal{AI}_{2n}(3214)|=M_n, ∣AI2n−1(3214)∣=∣RAI2n−1(1432)∣=Mn−Mn−2,|\mathcal{AI}_{2n-1}(3214)|=|\mathcal{RAI}_{2n-1}(1432)|=M_n-M_{n-2}, ∣RAI2n(1432)∣=∣RAI2n(3214)∣=Mn,|\mathcal{RAI}_{2n}(1432)|=|\mathcal{RAI}_{2n}(3214)|=M_n,

and

∣AI2n+1(1432)∣=∣RAI2n+1(3214)∣=Mn.|\mathcal{AI}_{2n+1}(1432)|=|\mathcal{RAI}_{2n+1}(3214)|=M_n.

These are attributed to Barnabei, Bonetti, Castronuovo, and Silimbani; the supplied text gives no resolution status.

References

Primary source

Sherry H. F. Yan, Lintong Wang and Robin D. P. Zhou, “On Refinements of Wilf-Equivalence for Involutions”, arXiv:2212.01800 (2022).

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