Bsila–Cox–Hugo–Styron–Zhuang fixed–pixed points equidistribution conjecture

From papers

Let P\mathcal P be the family

P={{132,312},{132,321},{213,231},{123,132,312},{123,213,231},{123,312,321},{132,312,321},{213,231,312},{213,231,321}}.\mathcal P= \left\{ \begin{array}{ccc} \{132,312\}, & \{132,321\}, & \{213,231\},\\[2mm] \{123,132,312\}, & \{123,213,231\}, & \{123,312,321\},\\[2mm] \{132,312,321\}, & \{213,231,312\}, & \{213,231,321\} \end{array} \right\}.

For ΠP\Pi\in\mathcal P, let Sn(Π)\mathfrak S_n(\Pi) denote the permutations of length nn avoiding every pattern in Π\Pi, and let fix\operatorname{fix} and pix\operatorname{pix} be the fixed-point and pixed-point statistics, respectively. Bsila–Cox–Hugo–Styron–Zhuang conjecture. For all n0n\geq 0 and every ΠP\Pi\in\mathcal P, the statistics fix\operatorname{fix} and pix\operatorname{pix} are equidistributed over Sn(Π)\mathfrak S_n(\Pi). Equivalently,

πSn(Π)xfix(π)=πSn(Π)xpix(π).\sum_{\pi\in\mathfrak S_n(\Pi)} x^{\operatorname{fix}(\pi)}=\sum_{\pi\in\mathfrak S_n(\Pi)} x^{\operatorname{pix}(\pi)}.

The conjecture concerns a common refinement of enumeration for restricted permutations and desarrangements. The source notes that Zhuang and his students independently obtained a bijective proof of the original conjecture, so the status of this formulation should be checked against that result.

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Sources & referencesView supporting material

Primary source

Yao Dong and Chao Xu, “A Refinement of the Fixed–Pixed Points Equidistribution on restricted Permutations”, arXiv:2606.00646 (2026).

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