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A052678
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Expansion of e.g.f. x^3/(1-3*x).
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1
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0, 0, 0, 6, 72, 1080, 19440, 408240, 9797760, 264539520, 7936185600, 261894124800, 9428188492800, 367699351219200, 15443372751206400, 694951773804288000, 33357685142605824000, 1701241942272897024000
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OFFSET
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0,4
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LINKS
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FORMULA
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E.g.f.: x^3/(1 - 3*x).
Recurrence: a(0)=0, a(1)=0, a(2)=0, a(3)=6, a(n) = 3*n*a(n-1).
a(n) = 3^(n-3)*n!, n>2.
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MAPLE
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spec := [S, {S=Prod(Z, Z, Z, Sequence(Union(Z, Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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MATHEMATICA
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Table[If[n<3, 0, 3^(n-3)*n!], {n, 0, 30}] (* G. C. Greubel, Jun 11 2022 *)
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PROG
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(SageMath) [0, 0, 0]+[3^(n-3)*factorial(n) for n in (3..30)] # G. C. Greubel, Jun 11 2022
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CROSSREFS
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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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