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A052598
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E.g.f. (1-x)/(1-x-2x^2).
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0
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1, 0, 4, 12, 144, 1200, 15840, 211680, 3467520, 61689600, 1241049600, 27223257600, 654316185600, 16999766784000, 476167826534400, 14282419447296000, 457079267893248000, 15539983733514240000
(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 543
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FORMULA
| E.g.f.: (-1+x)/(-1+x+2*x^2)
Recurrence: {a(1)=0, a(0)=1, (-2*n^2-6*n-4)*a(n)+(-2-n)*a(n+1)+a(n+2)=0}
Sum(1/9*(-1+5*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z+2*_Z^2))*n!
a(n) = n!*A078008(n). - R. J. Mathar, Nov 27 2011
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MAPLE
| spec := [S, {S=Sequence(Prod(Z, Sequence(Z), Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A204321 A152121 A077611 * A032071 A173603 A175718
Adjacent sequences: A052595 A052596 A052597 * A052599 A052600 A052601
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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