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 A052597 E.g.f. 1/(1-x^2-x^3). 0
 1, 0, 2, 6, 24, 240, 1440, 15120, 161280, 1814400, 25401600, 359251200, 5748019200, 99632332800, 1830744115200, 36614882304000, 774143225856000, 17428683976704000, 416154290872320000, 10461478635159552000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 542 FORMULA E.g.f.: -1/(-1+x^2+x^3) Recurrence: {a(1)=0, a(0)=1, a(2)=2, (-11*n-6-n^3-6*n^2)*a(n) +(-n^2-5*n-6)*a(n+1) +a(n+3)=0} Sum(-1/23*(-3-7*_alpha+2*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(_Z^3+_Z^2-1))*n! a(n) = n!*A000931(n+3). - R. J. Mathar, Nov 27 2011 MAPLE spec := [S, {S=Sequence(Prod(Z, Union(Z, Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); CROSSREFS Sequence in context: A034874 A052699 A074351 * A052632 A052692 A052723 Adjacent sequences:  A052594 A052595 A052596 * A052598 A052599 A052600 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 STATUS approved

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