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arXiv 2108.04302math.CO
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弱序的受限生成树

Restricted generating trees for weak orderings

Daniel Birmajer, Juan B. Gil, David S. Kenepp, Michael D. Weiner

AI总结:

本文研究由受限有根树叶子生成的弱序链的计数,关注大小为2和3的停止条件,并联系到几乎避免模式的排列的下降统计量。

摘要:

受排列和有序分拆中模式避免研究的启发,我们考虑由某些受限有根树的叶子所得到的弱序链的计数。一棵$n$阶树通过在每一步向每个节点插入一个新变量来生成。一个节点要么在$n$步之后成为叶子,要么在满足某个停止条件时成为叶子。本文关注大小为2的条件($x=y$,$x<y$,或$x\le y$)以及若干大小为3的条件。这里考虑的一些情形引出了对某些“几乎”避免模式的排列的下降统计量的研究。

英文摘要:

Motivated by the study of pattern avoidance in the context of permutations and ordered partitions, we consider the enumeration of weak-ordering chains obtained as leaves of certain restricted rooted trees. A tree of order $n$ is generated by inserting a new variable into each node at every step. A node becomes a leaf either after $n$ steps or when a certain stopping condition is met. In this paper we focus on conditions of size 2 ($x=y$, $x<y$, or $x\le y$) and several conditions of size 3. Some of the cases considered here lead to the study of descent statistics of certain `almost' pattern-avoiding permutations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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