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 A052623 E.g.f. x(1-x)^2/(1-3x+x^2). 0
 0, 1, 2, 18, 192, 2520, 39600, 725760, 15200640, 358162560, 9376819200, 270037152000, 8483597337600, 288734500454400, 10582834303641600, 415593298568448000, 17408598098411520000, 774797125808369664000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 569 FORMULA E.g.f.: x*(-1+x)^2/(1-3*x+x^2) Recurrence: {a(1)=1, a(0)=0, a(2)=2, (n^2+3*n+2)*a(n)+(-6-3*n)*a(n+1)+a(n+2)=0, a(3)=18} Sum(-1/5*(-3+7*_alpha)*_alpha^(-1-n), _alpha=RootOf(_Z^2-3*_Z+1))*n! MAPLE spec := [S, {S=Prod(Z, Sequence(Prod(Z, Sequence(Z), Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); CROSSREFS Sequence in context: A279860 A138413 A066274 * A155542 A157765 A156341 Adjacent sequences:  A052620 A052621 A052622 * A052624 A052625 A052626 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 STATUS approved

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Last modified January 20 14:40 EST 2019. Contains 319333 sequences. (Running on oeis4.)