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

From papers

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=0n/2n!k!(k+1)!(n2k)!.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, AI2n1(3214)=RAI2n1(1432)=MnMn2,|\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.

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Sources & referencesView supporting material

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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