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Search: id:A052897
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| 1, 2, 8, 44, 304, 2512, 24064, 261536, 3173888, 42483968, 621159424, 9841950208, 167879268352, 3065723549696, 59651093528576, 1231571119812608, 26883546193002496, 618463501807058944
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 873
N. J. A. Sloane, Transforms
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FORMULA
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E.g.f.: exp(2*x/(1-x)) - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 04 2001
Recurrence: {a(0)=1, a(1)=2, (n^2+n)*a(n)+(-4-2*n)*a(n+1)+a(n+2)}
LAH transform of A000079: a(n) = Sum_{k=0..n) 2^k*n!/k!*binomial(n-1, k-1). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Oct 17 2003
a(n)=n!*LaguerreL(n,-1,-2) - Karol A. Penson (penson(AT)lptl.jussieu.fr), Oct 16 2006
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MAPLE
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spec := [S, {B=Set(C), C=Sequence(Z, 1 <= card), S=Prod(B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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MATHEMATICA
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Range[0, 19]! CoefficientList[ Series[E^(2*x/(1 - x)), {x, 0, 19}], x] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 21 2007
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CROSSREFS
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Row sums of A059110.
Cf. A025168.
Sequence in context: A112912 A124467 A075792 this_sequence A137984 A005649 A005363
Adjacent sequences: A052894 A052895 A052896 this_sequence A052898 A052899 A052900
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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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