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A052613
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E.g.f. (1-2x)/(1-2x-x^2+x^3).
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0
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1, 0, 2, 6, 72, 720, 10080, 156240, 2822400, 56972160, 1280966400, 31654022400, 853580851200, 24932991283200, 784343085926400, 26435945023488000, 950417730662400000, 36304660098330624000, 1468365202287599616000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 558
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FORMULA
| E.g.f.: -(-1+2*x)/(x^3-x^2-2*x+1)
Recurrence: {a(1)=0, a(0)=1, a(2)=2, (n^3+6*n^2+11*n+6)*a(n) +(-n^2-5*n-6)*a(n+1) +(-2*n-6)*a(n+2) +a(n+3)=0}
Sum(1/7*(-1+3*_alpha)*_alpha^(-1-n), _alpha=RootOf(_Z^3-_Z^2-2*_Z+1))*n!
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MAPLE
| spec := [S, {S=Sequence(Prod(Z, Z, Sequence(Prod(Z, Sequence(Z)))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A195690 A171582 A152885 * A156493 A117515 A085865
Adjacent sequences: A052610 A052611 A052612 * A052614 A052615 A052616
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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