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A052579
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E.g.f. (2+x+x^2)/((1-x)(1+x+x^2)).
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0
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2, 1, 2, 12, 24, 120, 1440, 5040, 40320, 725760, 3628800, 39916800, 958003200, 6227020800, 87178291200, 2615348736000, 20922789888000, 355687428096000, 12804747411456000, 121645100408832000, 2432902008176640000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 523
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FORMULA
| E.g.f.: -(x^2+x+2)/(-1+x)/(1+x+x^2)
Recurrence: {a(1)=1, a(2)=2, a(0)=2, (-11*n-6-n^3-6*n^2)*a(n)+a(n+3)=0}
(4/3+Sum(1/3*_alpha^(-n), _alpha=RootOf(_Z^2+_Z+1)))*n!
a(n) = n!*A131534(n+1). - R. J. Mathar, Nov 27 2011
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MAPLE
| spec := [S, {S=Union(Sequence(Prod(Z, Z, Z)), Sequence(Z))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A077098 A069238 A165313 * A153908 A048296 A016542
Adjacent sequences: A052576 A052577 A052578 * A052580 A052581 A052582
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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