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Search: id:A036506
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| A036506 |
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Number of labeled 4-trees with n nodes. |
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+0
7
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| 0, 0, 0, 1, 1, 15, 455, 20230, 1166886, 82031250, 6768679170, 639276644655, 67876292150095, 7992910154350121, 1032869077119140625, 145221924661653841820, 22060305511905816000860, 3599313659344525384083060, 627583654087024080928783956
(list; graph; listen)
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OFFSET
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1,6
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REFERENCES
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F. Harary and E. Palmer, Graphical Enumeration, (1973), p. 30, Problem 1.13(b) with k=4.
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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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C(n,4)*(4*n-15)^(n-6).
Number of labeled k-trees on n nodes is binomial(n, k) * (k(n-k)+1)^(n-k-2).
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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: A020285 A041423 A041420 this_sequence A005815 A120600 A129892
Adjacent sequences: A036503 A036504 A036505 this_sequence A036507 A036508 A036509
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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