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Search: id:A052856
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| 1, 2, 4, 14, 76, 542, 4684, 47294, 545836, 7087262, 102247564, 1622632574, 28091567596, 526858348382, 10641342970444, 230283190977854, 5315654681981356, 130370767029135902, 3385534663256845324
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Stirling transform of A005212(n-1)=[1,1,0,6,0,120,0,...] is a(n-1)=[1,2,4,14,76,...]. - Michael Somos Mar 04 2004
Stirling transform of (-1)^n*A052612(n-1)=[0,2,-2,12,-24,...] is a(n-1)=[0,2,4,14,76,...]. - Michael Somos Mar 04 2004
Stirling transform of A000142(n)=[2,2,6,24,120,...] is a(n)=[2,2,4,14,76,...]. - Michael Somos Mar 04 2004
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 824
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FORMULA
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E.g.f.: (1-3*exp(x)+exp(x)^2)/(-2+exp(x))
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MAPLE
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spec := [S, {B=Sequence(C), C=Set(Z, 1 <= card), S=Union(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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PROGRAM
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(PARI) a(n)=if(n<0, 0, n!*polcoeff(subst(y+1/(1-y), y, exp(x+x*O(x^n))-1), n))
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CROSSREFS
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A000670(n)=a(n)-1, if n>0. A032109(n)=a(n)/2, if n>0.
Sequence in context: A032147 A007712 A075098 this_sequence A093462 A032052 A005737
Adjacent sequences: A052853 A052854 A052855 this_sequence A052857 A052858 A052859
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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