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In this paper we give a bijection between the class of permutations that can be drawn on an X-shape and a certain set of permutations that appears in [Knuth] in connection to sorting algorithms. A natural generalization of this set leads us…

Combinatorics · Mathematics 2007-10-29 Sergi Elizalde

The Eulerian polynomials $A_n(x)$ give the distribution of descents over permutations. It is also known that the distribution of descents over stack-sortable permutations (i.e. permutations sortable by a certain algorithm whose internal…

Combinatorics · Mathematics 2023-10-27 Sergey Kitaev , Philip B. Zhang

A permutation statistic $\operatorname{st}$ is said to be shuffle-compatible if the distribution of $\operatorname{st}$ over the set of shuffles of two disjoint permutations $\pi$ and $\sigma$ depends only on $\operatorname{st}\pi$,…

Combinatorics · Mathematics 2023-09-29 Jinting Liang , Bruce E. Sagan , Yan Zhuang

We extend Stanley's work on alternating permutations with extremal number of fixed points in two directions: first, alternating permutations are replaced by permutations with a prescribed descent set; second, instead of simply counting…

Combinatorics · Mathematics 2007-06-22 Guo-Niu Han , Guoce Xin

Claesson and Linusson [Proc. Am. Math. Soc., 139 (2011), 435-449] observed that there are n! matchings on [2n] with no left-nestings. Inspired by this result, this paper is devoted to exploring a deeper connection between matchings and…

Combinatorics · Mathematics 2026-02-03 Shi-Mei Ma , Sergey Kitaev , Jean Yeh , Yeong-Nan Yeh

We prove that the enumerative polynomials of generalized Stirling permutations by the statistics of plateaux, descents and ascents are partial $\gamma$-positive. Specialization of our result to the Jacobi-Stirling permutations confirms a…

Combinatorics · Mathematics 2020-05-15 Zhicong Lin , Jun Ma , Philip B. Zhang

In 1974, Carlitz and Scoville introduced the Stirling-Eulerian polynomial $A_n(x,y|\alpha,\beta)$ as the enumerator of permutations by descents, ascents, left-to-right maxima and right-to-left maxima. Recently, Ji considered a refinement of…

Combinatorics · Mathematics 2024-04-16 Yao Dong , Zhicong Lin , Qiongqiong Pan

In this research announcement we present a new q-analog of a classical formula for the exponential generating function of the Eulerian polynomials. The Eulerian polynomials enumerate permutations according to their number of descents or…

Combinatorics · Mathematics 2007-05-23 John Shareshian , Michelle L. Wachs

P.L. Erdos and L.A. Szekely [Adv. Appl. Math. 10(1989), 488-496] gave a bijection between rooted semilabeled trees and set partitions. L.H. Harper's results [Ann. Math. Stat. 38(1967), 410-414] on the asymptotic normality of the Stirling…

Combinatorics · Mathematics 2011-08-31 Eva Czabarka , Peter L. Erdos , Virginia Johnson , Anne Kupczok , Laszlo A. Szekely

We recover Gessel's determinantal formula for the generating function of permutations with no ascending subsequence of length m+1. The starting point of our proof is the recursive construction of these permutations by insertion of the…

Combinatorics · Mathematics 2025-09-26 Mireille Bousquet-Mélou

We study two generalizations of the gamma-expansion of Eulerian polynomials from the viewpoint of the decompositions of statistics. We first present an expansion formula of the trivariate Eulerian polynomials, which are the enumerators for…

Combinatorics · Mathematics 2021-11-18 Shi-Mei Ma , Jun Ma , Jean Yeh , Yeong-Nan Yeh

Physical and mathematical applications of fractional Poisson probability distribution have been presented. As a physical application, a new family of quantum coherent states has been introduced and studied. As mathematical applications, we…

Mathematical Physics · Physics 2015-05-13 Nick Laskin

The second Eulerian numbers are defined via the descent enumerator of Stirling permutations, a class of permutations introduced by Gessel and Stanley. We give a simple and conceptual proof of two identities relating the Bernoulli numbers…

Combinatorics · Mathematics 2026-05-26 Jack Boncompagni

Finding distributions of permutation statistics over pattern-avoiding classes of permutations attracted much attention in the literature. In particular, Bukata et al. found distributions of ascents and descents on permutations avoiding any…

Combinatorics · Mathematics 2024-11-06 Tian Han , Sergey Kitaev

Andr\'e proved that the number of alternating permutations on $\{1, 2, \dots, n\}$ is equal to the Euler number $E_n$. A refinement of Andr\'e's result was given by Entringer, who proved that counting alternating permutations according to…

Combinatorics · Mathematics 2022-03-22 Yoann Gelineau , Heesung Shin , Jiang Zeng

Permutations with bounded drop size, which we also call bounded permutations, was introduced by Chung, Claesson, Dukes and Graham. Petersen introduced a new Mahonian statistic the sorting index, which is denoted by $\sor$. Meanwhile, Wilson…

Combinatorics · Mathematics 2021-01-18 Joanna Na Chen , Robin Dapao Zhou

We study a family of polynomials associated with ascent-descent statistics on labeled rooted plane k-ary trees introduced by Gessel, from a rook-theoretic perspective. We generalize the excedance statistic on permutations to maximal…

Combinatorics · Mathematics 2016-04-26 Vasu Tewari

In this paper, we consider the number of occurrences of descents, ascents, 123-subwords, 321-subwords, peaks and valleys in flattened permutations, which were recently introduced by Callan in his study of finite set partitions. For descents…

Combinatorics · Mathematics 2013-07-16 Toufik Mansour , Mark Shattuck , David G. L. Wang

Normal approximations for descents and inversions of permutations of the set $\{1,2,...,n\}$ are well known. A number of sequences that occur in practice, such as the human genome and other genomes, contain many repeated elements. Motivated…

Probability · Mathematics 2014-08-28 Mark Conger , D. Viswanath

For any finite partially ordered set $P$, the $P$-Eulerian polynomial is the generating function for the descent number over the set of linear extensions of $P$, and is closely related to the order polynomial of $P$ arising in the theory of…

Combinatorics · Mathematics 2024-09-11 T. Kyle Petersen , Yan Zhuang