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 A052590 E.g.f. (1-x)/(1-4x+2x^2). 0
 1, 3, 20, 204, 2784, 47520, 973440, 23264640, 635443200, 19525847040, 666654105600, 25037094297600, 1025783842406400, 45529186384281600, 2176249118883840000, 111452688851632128000, 6088372509440212992000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 535 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 MAPLE spec := [S, {S=Sequence(Union(Z, Z, Prod(Z, Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); MATHEMATICA With[{nn=20}, CoefficientList[Series[(1-x)/(1-4x+2x^2), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jan 10 2014 *) CROSSREFS Sequence in context: A052595 A244491 A295100 * A081209 A196560 A257476 Adjacent sequences:  A052587 A052588 A052589 * A052591 A052592 A052593 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 STATUS approved

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Last modified August 8 14:59 EDT 2022. Contains 356009 sequences. (Running on oeis4.)