Conjecture on the number of distribution-equivalence classes of length-2 mesh patterns

From papers

Let p1p_1 and p2p_2 be mesh patterns of length 22. They are equivalent when sn,k(p1)=sn,k(p2)s_{n,k}(p_1)=s_{n,k}(p_2) for all n,k0n,k\geq0, where sn,k(p)s_{n,k}(p) counts nn-permutations containing exactly kk occurrences of pp. Distribution-class conjecture. There are exactly 105105 equivalence classes with respect to distribution for mesh patterns of length 22. The paper establishes bounds between 105105 and 108108 classes and presents this exact count as the remaining conjectural value.

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Primary source

Xinyu Su, Sergey Kitaev and Jiahao Zhang, “Equidistribution of mesh patterns of short length”, arXiv:2605.19429 (2026).

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