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A052644
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E.g.f. (1+3x-3x^2)/(1-x)^2.
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0
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1, 5, 12, 42, 192, 1080, 7200, 55440, 483840, 4717440, 50803200, 598752000, 7664025600, 105859353600, 1569209241600, 24845812992000, 418455797760000, 7469435990016000, 140852221526016000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 590
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FORMULA
| E.g.f.: -(-3*x+3*x^2-1)/(-1+x)^2
Recurrence: {a(0)=1, a(1)=5, (-n^2-6*n-5)*a(n)+(n+4)*a(n+1)=0, a(2)=12}
(n+4)*n!, n>0.
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MAPLE
| spec := [S, {S=Prod(Sequence(Z), Union(Z, Z, Z, Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A082189 A129795 A187916 * A052280 A195541 A006078
Adjacent sequences: A052641 A052642 A052643 * A052645 A052646 A052647
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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