Weak-excedance mid-points and cycle descents

From papers

Let SnS_n be the set of permutations of [n][n]. Consider the statistic counting weak excedances that are also mid-points of a decreasing subsequence of length 33 (Statistic 373373), and let the cycle descent number be Statistic 317317.

Weak-excedance mid-point conjecture. The number of weak excedances that are also mid-points of a decreasing subsequence of length 33 (Statistic 373373) is equidistributed with the cycle descent number (Statistic 317317) and thus exhibits the cyclic sieving phenomenon under involutions with 2n12^{n-1} fixed points.

This is stated among the paper's conjectured cyclic-sieving instances and was tested up to n=10n=10; the paper supplies no proof or resolution in the provided material.

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Sources & referencesView supporting material

Primary source

Ashleigh Adams, Jennifer Elder, Nadia Lafrenière, Erin McNicholas, Jessica Striker and Amanda Welch, “Cyclic sieving on permutations – an analysis of maps and statistics in the FindStat database”, arXiv:2402.16251 (2025).

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