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arXiv 0906.1672math.CO
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路图与Stirling置换

On Path diagrams and Stirling permutations

Markus Kuba, Anna L. Varvak

摘要:

排列可以根据四种局部类型进行局部分类:峰、谷、双上升和双下降。对应的二叉增树分类使用四种不同类型的节点。Flajolet证明了局部类型生成函数的连分数表示,使用了置换之间的经典双射、二元递增树和由Motzkin路径诱导的适当定义的路径图。本文的目的是将局部类型的概念从置换扩展到$k$ -Stirling置换(也称为$k$ -多重置换)。我们建立了这些局部类型到$(k+1)$ -元增树的节点类型的双射。我们提出了一个分支连分数表示这些本地类型的生成函数,通过双射与路径图诱导的pakukasiewicz路径,推广的结果从排列到任意的$k$ -斯特林排列。利用非标准增树、$k$ -Stirling置换和路径图之间的对应关系,进一步证明了普通Stirling置换的母函数至少有三个分支连分数表示.

英文摘要:

A permutation can be locally classified according to the four local types: peaks, valleys, double rises and double falls. The corresponding classification of binary increasing trees uses four different types of nodes. Flajolet demonstrated the continued fraction representation of the generating function of local types, using a classical bijection between permutations, binary increasing trees, and suitably defined path diagrams induced by Motzkin paths. The aim of this article is to extend the notion of local types from permutations to $k$-Stirling permutations (also known as $k$-multipermutations). We establish a bijection of these local types to node types of $(k+1)$-ary increasing trees. We present a branched continued fraction representation of the generating function of these local types through a bijection with path diagrams induced by Łukasiewicz paths, generalizing the results from permutations to arbitrary $k$-Stirling permutations. We further show that the generating function of ordinary Stirling permutation has at least three branched continued fraction representations, using correspondences between non-standard increasing trees, $k$-Stirling permutations and path diagrams.

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