{"title":"Descent generating polynomials for (n−3)- and (n−4)-stack-sortable (pattern-avoiding) permutations","authors":"Philip B. Zhang , Sergey Kitaev","doi":"10.1016/j.dam.2025.03.032","DOIUrl":null,"url":null,"abstract":"<div><div>In this paper, we find distribution of descents over <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>3</mn><mo>)</mo></mrow></math></span>- and <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>4</mn><mo>)</mo></mrow></math></span>-stack-sortable permutations in terms of Eulerian polynomials. Our results generalize the enumeration results by Claesson, Dukes, and Steingrímsson on <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>3</mn><mo>)</mo></mrow></math></span>- and <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>4</mn><mo>)</mo></mrow></math></span>-stack-sortable permutations. Moreover, we find distribution of descents on <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>2</mn><mo>)</mo></mrow></math></span>-, <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>3</mn><mo>)</mo></mrow></math></span>- and <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>4</mn><mo>)</mo></mrow></math></span>-stack-sortable permutations that avoid any given pattern of length 3, which extends known results in the literature on distribution of descents over pattern-avoiding 1- and 2-stack-sortable permutations. Our distribution results also give enumeration of <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>2</mn><mo>)</mo></mrow></math></span>-, <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>3</mn><mo>)</mo></mrow></math></span>- and <span><math><mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>4</mn><mo>)</mo></mrow></math></span>-stack-sortable permutations avoiding any pattern of length 3. One of our conjectures links our work to stack-sorting with restricted stacks, and the other conjecture states that 213-avoiding permutations sortable with <span><math><mi>t</mi></math></span> stacks are equinumerous with 321-avoiding permutations sortable with <span><math><mi>t</mi></math></span> stacks for any <span><math><mi>t</mi></math></span>.</div></div>","PeriodicalId":50573,"journal":{"name":"Discrete Applied Mathematics","volume":"372 ","pages":"Pages 1-14"},"PeriodicalIF":1.0000,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Discrete Applied Mathematics","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0166218X25001568","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS, APPLIED","Score":null,"Total":0}
引用次数: 0
Abstract
In this paper, we find distribution of descents over - and -stack-sortable permutations in terms of Eulerian polynomials. Our results generalize the enumeration results by Claesson, Dukes, and Steingrímsson on - and -stack-sortable permutations. Moreover, we find distribution of descents on -, - and -stack-sortable permutations that avoid any given pattern of length 3, which extends known results in the literature on distribution of descents over pattern-avoiding 1- and 2-stack-sortable permutations. Our distribution results also give enumeration of -, - and -stack-sortable permutations avoiding any pattern of length 3. One of our conjectures links our work to stack-sorting with restricted stacks, and the other conjecture states that 213-avoiding permutations sortable with stacks are equinumerous with 321-avoiding permutations sortable with stacks for any .
期刊介绍:
The aim of Discrete Applied Mathematics is to bring together research papers in different areas of algorithmic and applicable discrete mathematics as well as applications of combinatorial mathematics to informatics and various areas of science and technology. Contributions presented to the journal can be research papers, short notes, surveys, and possibly research problems. The "Communications" section will be devoted to the fastest possible publication of recent research results that are checked and recommended for publication by a member of the Editorial Board. The journal will also publish a limited number of book announcements as well as proceedings of conferences. These proceedings will be fully refereed and adhere to the normal standards of the journal.
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