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A052763
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Number of rooted trees with n nodes and 4-colored non-root nodes.
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6
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0, 1, 4, 26, 188, 1499, 12628, 111064, 1006840, 9345761, 88371580, 848273424, 8244075700, 80959901281, 802137370804, 8008422811882, 80488941119484, 813703130213745, 8268866850613468, 84417609311862182, 865408913186449784, 8905028017997573696
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OFFSET
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0,3
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COMMENTS
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Previous name was: A simple grammar.
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LINKS
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FORMULA
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a(n) ~ c * d^n / n^(3/2), where d = 11.0699628777593263124193026233177403862890348..., c = 0.1016234204063820357399566577477318256736416... . - Vaclav Kotesovec, Aug 26 2014
G.f. A(x) satisfies: A(x) = x*exp(4*Sum_{k>=1} A(x^k)/k). - Ilya Gutkovskiy, Mar 19 2018
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MAPLE
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spec := [S, {B=Set(S), S=Prod(Z, B, B, B, B)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
with(numtheory):
a:= proc(n) option remember; `if`(n<2, n, (add(add(d*
a(d), d=divisors(j))*a(n-j)*4, j=1..n-1))/(n-1))
end:
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MATHEMATICA
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a[n_] := a[n] = If[n<2, n, Sum[Sum[d*a[d], {d, Divisors[j]}]*a[n-j]*4, {j, 1, n-1}]/(n-1)]; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Feb 24 2016, adapted from Maple *)
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CROSSREFS
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KEYWORD
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easy,nonn,eigen
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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EXTENSIONS
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STATUS
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approved
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