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 A052684 E.g.f. 1/(1-2x^2-x^3). 0
 1, 0, 4, 6, 96, 480, 6480, 60480, 887040, 11975040, 203212800, 3512678400, 69455232000, 1444668825600, 32953394073600, 796373690112000, 20671716409344000, 567677135241216000, 16550136029306880000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 632 FORMULA E.g.f.: -1/(-1+2*x^2+x^3) Recurrence: {a(1)=0, a(0)=1, a(2)=4, (-11*n-6-n^3-6*n^2)*a(n)+(-2*n^2-10*n-12)*a(n+1)+a(n+3)=0} Sum(1/5*(-6+7*_alpha+8*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z^2+_Z^3))*n! a(n) = n!*A008346(n). - R. J. Mathar, Nov 27 2011 MAPLE spec := [S, {S=Sequence(Prod(Z, Union(Z, Z, Prod(Z, Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); MATHEMATICA With[{nn=20}, CoefficientList[Series[1/(1-2x^2-x^3), {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Apr 22 2012 *) CROSSREFS Sequence in context: A222495 A307101 A087934 * A213128 A105037 A139730 Adjacent sequences:  A052681 A052682 A052683 * A052685 A052686 A052687 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 STATUS approved

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Last modified May 26 22:58 EDT 2020. Contains 334634 sequences. (Running on oeis4.)