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Search: id:A004114
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| A004114 |
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Number of trees with n nodes and 2-colored internal (non-leaf) nodes.
(Formerly M1422)
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+0
4
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| 1, 1, 1, 2, 5, 12, 33, 98, 305, 1002, 3424, 12016, 43230, 158516, 590621, 2230450, 8521967, 32889238, 128064009, 502590642, 1986357307, 7900377892, 31602819524, 127076645038, 513419837168, 2083414420394, 8488377206876
(list; graph; listen)
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OFFSET
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0,4
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
F. Harary, R. W. Robinson and A. J. Schwenk, Twenty-step algorithm for determining the asymptotic number of trees of various species, J. Austral. Math. Soc., Series A, 20 (1975), 483-503. Errata: Vol. A 41 (1986), p. 325.
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LINKS
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Index entries for sequences related to trees
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FORMULA
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G.f.: 1+B(x)-x*B(x)-B(x)^2/2+B(x^2)/2 where B(x) is g.f. of A004113.
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CROSSREFS
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Cf. A004113, A052316, A052317.
Sequence in context: A000560 A032124 A000669 this_sequence A076864 A032292 A151408
Adjacent sequences: A004111 A004112 A004113 this_sequence A004115 A004116 A004117
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms, formula and new description from Christian G. Bower (bowerc(AT)usa.net), Dec 15 1999.
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