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Search: id:A006965
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| A006965 |
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Number of directed trees with n nodes.
(Formerly M1677)
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+0
3
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| 1, 2, 6, 25, 114, 591, 3298, 19532, 120687, 771373, 5061741, 33943662, 231751331, 1606587482, 11283944502, 80157645245, 575105238243, 4162624144308, 30365913761136, 223075674659696, 1649166676341180, 12262121068089094
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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P. Leroux and B. Miloudi, ``G\'{e}n\'{e}ralisations de la formule d'Otter,'' Ann. Sci. Math. Qu\'{e}bec, Vol. 16, No. 1, pp. 53-80, 1992.
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LINKS
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P. Leroux and B. Miloudi, Generalisations de la formule d'Otter, Ann. Sci. Math. Quebec 16 (1992), no 1, 53-80.
Index entries for sequences related to trees
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MAPLE
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with(combstruct):B:=x->add(3*count([S, {B = Set(S), S = Prod(B, B, B, Z)}, unlabeled], size=i)*x^i, i=1..50); seq(coeff(B(x)-B(x)^2/2+B(x^2)/2, x, n)/3, n=1..30); # with Algolib (Pab Ter)
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CROSSREFS
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Equals (1/3) A038060(n).
Adjacent sequences: A006962 A006963 A006964 this_sequence A006966 A006967 A006968
Sequence in context: A074418 A003454 A014277 this_sequence A058801 A074010 A030806
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KEYWORD
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nonn
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AUTHOR
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Simon Plouffe (plouffe(AT)math.uqam.ca)
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