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A052590
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E.g.f. (1-x)/(1-4x+2x^2).
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0
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1, 3, 20, 204, 2784, 47520, 973440, 23264640, 635443200, 19525847040, 666654105600, 25037094297600, 1025783842406400, 45529186384281600, 2176249118883840000, 111452688851632128000, 6088372509440212992000
(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 535
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FORMULA
| E.g.f.: -(-1+x)/(1-4*x+2*x^2)
Recurrence: {a(0)=1, a(1)=3, (2*n^2+6*n+4)*a(n)+(-4*n-8)*a(n+1)+a(n+2)=0}
Sum(1/4*_alpha^(-1-n), _alpha=RootOf(1-4*_Z+2*_Z^2))*n!
a(n) =n!*A007052(n). - R. J. Mathar, Nov 27 2011
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MAPLE
| spec := [S, {S=Sequence(Union(Z, Z, Prod(Z, Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A158833 A054361 A052595 * A081209 A196560 A014068
Adjacent sequences: A052587 A052588 A052589 * A052591 A052592 A052593
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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