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arXiv · 2609.14386

The (p,q)-Analogues of Bi-Stirling Eulerian Polynomials via continued fractions

Chao Xu·Jiang Zeng
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Abstract

We establish Jacobi-type continued fraction expansions for (p,q)-analogues of the bi-Stirling Eulerian polynomials, which refine classical Eulerian statistics on permutations. These polynomials admit equivalent definitions in terms of descents or excedances. The parameters p and q encode refined permutation statistics, including (ldes,rasc) and (cros,nest). Our approach is based on weighted Motzkin path models arising from variants of the bijections of Françon--Viennot and Foata--Zeilberger. As applications, we obtain new results on total positivity and gamma-positivity for several families of enumerative polynomials. Our results unify and extend a number of recent works in the literature.

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Chao Xu, Jiang Zeng. 2026-09-13. The (p,q)-Analogues of Bi-Stirling Eulerian Polynomials via continued fractions. https://arxiv.org/abs/2609.14386

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