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Search: id:A036657
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| A036657 |
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Number of n-node rooted unlabeled trees with out-degree <=2 and exactly 2 edges at the root. |
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3
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| 0, 0, 0, 1, 1, 3, 5, 12, 23, 52, 109, 244, 532, 1196, 2671, 6055, 13726, 31380, 71901, 165635, 382610, 887215, 2062777, 4810230, 11243898, 26346341, 61863991, 145560102, 343121676, 810246372, 1916417479, 4539722153, 10769366928
(list; graph; listen)
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OFFSET
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0,6
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REFERENCES
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S. J. Cyvin et al., Enumeration of constitutional isomers of polyenes, J. Molec. Structure (Theochem), 357 (1995), 255-261.
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LINKS
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Index entries for sequences related to rooted trees
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FORMULA
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G.f. satisfies A(x) = (W(x)-x)*(1-x)/x-x, where W(x) is g.f. for A001190.
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MAPLE
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N := 40: G036657 := series(G001190*(1/x-1)-1, x, N); A036657 := n->coeff(G036657, x, n);
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CROSSREFS
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First differences of A001190.
Adjacent sequences: A036654 A036655 A036656 this_sequence A036658 A036659 A036660
Sequence in context: A161624 A034758 A131322 this_sequence A047761 A026786 A027246
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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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