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A052625
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E.g.f. (1-x)^2/(1-2x+x^2-x^3).
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0
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1, 0, 0, 6, 48, 360, 3600, 45360, 645120, 10160640, 177811200, 3432844800, 72329241600, 1650160512000, 40537905408000, 1067062284288000, 29961435119616000, 893842506805248000, 28234468042260480000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 571
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FORMULA
| E.g.f.: -(-1+x)^2/(-1+2*x-x^2+x^3)
Recurrence: {a(1)=0, a(0)=1, a(2)=0, (-11*n-6-n^3-6*n^2)*a(n) +(n^2+5*n+6)*a(n+1) +(-2*n-6)*a(n+2) +a(n+3)=0}
Sum(-1/23*(2-11*_alpha+6*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z-_Z^2+_Z^3))*n!
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MAPLE
| spec := [S, {S=Sequence(Prod(Z, Z, Z, Sequence(Z), Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A049316 A024075 A052571 * A155130 A083233 A002918
Adjacent sequences: A052622 A052623 A052624 * A052626 A052627 A052628
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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