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arXiv · 1210.3799

Some remarks on the joint distribution of descents and inverse descents

Mirkó Visontai
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Abstract

We study the joint distribution of descents and inverse descents over the set of permutations of n letters. Gessel conjectured that the two-variable generating function of this distribution can be expanded in a given basis with nonnegative integer coefficients. We investigate the action of the Eulerian operators that give the recurrence for these generating functions. As a result we devise a recurrence for the coefficients but are unable to settle the conjecture. We examine generalizations of the conjecture and obtain a type B analog of the recurrence satisfied by the two-variable generating function. We also exhibit some connections to cyclic descents and cyclic inverse descents. Finally, we propose a combinatorial model in terms of statistics on inversion sequences.

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Mirkó Visontai. 2012-10-14. Some remarks on the joint distribution of descents and inverse descents. https://arxiv.org/abs/1210.3799

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