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A052697
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E.g.f. 1/(1-x^3-x^4).
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0
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1, 0, 0, 6, 24, 0, 720, 10080, 40320, 362880, 10886400, 119750400, 958003200, 24908083200, 523069747200, 6538371840000, 125536739328000, 3556874280960000, 70426110763008000, 1338096104497152000
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OFFSET
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0,4
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LINKS
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Table of n, a(n) for n=0..19.
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 646
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FORMULA
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E.g.f.: -1/(-1+x^3+x^4)
Recurrence: {a(1)=0, a(0)=1, a(2)=0, a(3)=6, (-n^4-35*n^2-50*n-24-10*n^3)*a(n)+(-n^3-9*n^2-26*n-24)*a(n+1)+a(n+4)=0}
Sum(-1/283*(-16-73*_alpha+3*_alpha^2+12*_alpha^3)*_alpha^(-1-n), _alpha=RootOf(-1+_Z^3+_Z^4))*n!
a(n) = n!*A017817(n). - R. J. Mathar, Nov 27 2011
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Z, Union(Z, Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A013266 A154420 A194770 * A213344 A193429 A213278
Adjacent sequences: A052694 A052695 A052696 * A052698 A052699 A052700
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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STATUS
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approved
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