arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2010.14902math.CO
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树木和周期

Trees and cycles

Peter J. Cameron, Liam Stott

摘要:

设$T$是$n$顶点上的树。我们可以把$T$的边看作顶点集的转置;它们的乘积(以任何顺序)是一个轮换。所有可能的轮换出现(每一个都只出现一次)当且仅当树是一个星形。在本文中,我们发现的实现循环的数量,并获得一些结果的数量实现的每个循环,为其他树。我们还解决了逆问题的树木,从而产生一个给定的周期的数量。在这个过程中,我们遇到了一些熟悉的数列,包括欧拉数和Fuss-Catalan数。

英文摘要:

Let $T$ be a tree on $n$ vertices. We can regard the edges of $T$ as transpositions of the vertex set; their product (in any order) is a cyclic permutation. All possible cyclic permutations arise (each exactly once) if and only if the tree is a star. In this paper we find the number of realised cycles, and obtain some results on the number of realisations of each cycle, for other trees. We also solve the inverse problem of the number of trees which give rise to a given cycle. On the way, we meet some familiar number sequences including the Euler and Fuss--Catalan numbers.

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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