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Burstein’s permutation conjecture, Hong and Li’s inversion sequence conjecture and restricted Eulerian distributions

Published online by Cambridge University Press:  23 October 2023

Shane Chern
Affiliation:
Department of Mathematics and Statistics, Dalhousie University, Halifax, NS, Canada (chenxiaohang92@gmail.com; xh375529@dal.ca)
Shishuo Fu
Affiliation:
College of Mathematics and Statistics, Chongqing University, Huxi Campus, Chongqing, P.R. China (fsshuo@cqu.edu.cn)
Zhicong Lin
Affiliation:
Research Center for Mathematics and Interdisciplinary Sciences, Shandong University, Qingdao, Shandong, P.R. China (linz@sdu.edu.cn)

Abstract

Recently, Hong and Li launched a systematic study of length-four pattern avoidance in inversion sequences, and in particular, they conjectured that the number of 0021-avoiding inversion sequences can be enumerated by the OEIS entry A218225. Meanwhile, Burstein suggested that the same sequence might also count three sets of pattern-restricted permutations. The objective of this paper is not only a confirmation of Hong and Li’s conjecture and Burstein’s first conjecture but also two more delicate generating function identities with the $\mathsf{ides}$ statistic concerned in the restricted permutation case and the $\mathsf{asc}$ statistic concerned in the restricted inversion sequence case, which yield a new equidistribution result.

Type
Research Article
Copyright
© The Author(s), 2023. Published by Cambridge University Press on Behalf of The Edinburgh Mathematical Society.

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