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arXiv 0902.2274math.CO
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任意固定整数长度的一维块的棱锥的Enumeration

Enumeration of pyramids of one-dimensional pieces of arbitrary fixed integer length

Bergfinnur Durhuus, Soren Eilers

摘要:

我们考虑由固定整数长度a的一维片段组成的金字塔,它们可以有从1到a的整数长度的成对重叠。我们证明了大小为m的金字塔的数量,即由m个部分组成,对于每个a >= 2,等于(am-1,m-1)。这推广了a = 2的一个众所周知的结果。指出了所谓的右(或左)金字塔与a叉树之间的双射对应,并证明了金字塔的平均宽度与其大小的平方根成正比.

英文摘要:

We consider pyramids made of one-dimensional pieces of fixed integer length a and which may have pairwise overlaps of integer length from 1 to a. We prove that the number of pyramids of size m, i.e. consisting of m pieces, equals (am-1,m-1) for each a >= 2. This generalises a well known result for a = 2. A bijective correspondence between so-called right (or left) pyramids and a-ary trees is pointed out, and it is shown that asymptotically the average width of pyramids is proportional to the square root of the size.

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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