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A097628
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Number of rooted directed trees on n nodes with a green root.
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1
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0, 2, 15, 232, 4535, 114276, 3478083, 124625040, 5135162607, 239298611020, 12443586907763, 714352426078776, 44874695909075799, 3061971330141166548, 225519631138748009955, 17832309102333780001312
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OFFSET
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1,2
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COMMENTS
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Ditrees are well-colored directed trees. Well-colored means, each green vertex has at least a red child, each red vertex has no red child.
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LINKS
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FORMULA
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E.g.f.: A(x) = C(2x)/2+C(-C(2x)/2), C(x) = e.g.f. of A000169.
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MATHEMATICA
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terms = 16;
c[x_] = -LambertW[-x];
A[x_] = c[2x]/2 + c[-c[2x]/2];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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