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A052696
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Expansion of e.g.f. (1-x)^2/(1-4*x+3*x^2-x^3).
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1
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1, 2, 12, 114, 1440, 22680, 428400, 9439920, 237726720, 6735052800, 212012640000, 7341338188800, 277317497318400, 11348577278438400, 500138456661043200, 23615780481925632000, 1189441481702842368000
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OFFSET
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0,2
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LINKS
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G. C. Greubel, Table of n, a(n) for n = 0..375
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 645
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FORMULA
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E.g.f.: (1 - x)^2/(1 - 4*x + 3*x^2 - x^3).
D-finite recurrence: a(0)=1, a(1)=2, a(2)=12, a(n) = 2*n*a(n-1) - 3*n*(n-1)*a(n-2) + n*(n-1)*(n-2)*a(n-3).
a(n) = n! * Sum_{alpha=RootOf(-1 +4*Z -3*Z^2 +Z^3)} (1/31)*(4 + 7*alpha - 2*alpha^2)*alpha^(-1-n).
a(n) = n! * A052544(n). - G. C. Greubel, May 31 2022
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MAPLE
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spec := [S, {S=Sequence(Union(Z, Prod(Z, Sequence(Z), Sequence(Z))))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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MATHEMATICA
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With[{nn=20}, CoefficientList[Series[(1-x)^2/(1-4x+3x^2-x^3), {x, 0, nn}], x]Range[0, nn]!] (* Harvey P. Dale, Aug 28 2012 *)
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PROG
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(Magma) R<x>:=PowerSeriesRing(Rationals(), 30);
Coefficients(R!(Laplace( (1-x)^2/(1-4*x+3*x^2-x^3) ))); // G. C. Greubel, May 31 2022
(SageMath)
@CachedFunction
def b(n): # b = A052544
if (n<3): return factorial(n+1)
else: return 4*b(n-1) - 3*b(n-2) + b(n-3)
def A052696(n): return factorial(n)*b(n)
[A052696(n) for n in (0..40)] # G. C. Greubel, May 31 2022
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CROSSREFS
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Cf. A052544.
Sequence in context: A091854 A141141 A128571 * A107723 A258175 A225797
Adjacent sequences: A052693 A052694 A052695 * A052697 A052698 A052699
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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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