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Search: id:A036361
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| A036361 |
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Number of labeled 2-trees with n nodes. |
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+0
6
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| 0, 1, 1, 6, 70, 1215, 27951, 799708, 27337500, 1086190605, 49162945645, 2496308717826, 140489907594114, 8678436279296875, 583701359488329915, 42457773984656284920, 3320786296452525792376, 277898747312921495246937, 24775177557380767822265625
(list; graph; listen)
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OFFSET
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1,4
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REFERENCES
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L. W. Beineke, R. E. Pippert, The number of labeled k-dimensional trees, J. Combinatorial Theory 6 1969 200-205. Math. Rev. 38 #3182.
F. Harary and E. Palmer, Graphical Enumeration, (1973), p. 30.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..100
Index entries for sequences related to trees
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FORMULA
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Number of labeled k-trees on n nodes is binomial(n, k) * (k(n-k)+1)^(n-k-2).
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MAPLE
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A036361 := n-> binomial(n, 2)*(2*n-3)^(n-4);
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CROSSREFS
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Cf. A000272 (labeled trees), A036361 (labeled 2-trees), A036362 (labeled 3-trees), A036506 (labeled 4-trees), A000055 (unlabeled trees), A054581 (unlabeled 2-trees).
Sequence in context: A104900 A001448 A024489 this_sequence A050788 A027317 A099339
Adjacent sequences: A036358 A036359 A036360 this_sequence A036362 A036363 A036364
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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