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A051604
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a(n) = (3*n+4)!!!/4!!!.
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10
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1, 7, 70, 910, 14560, 276640, 6086080, 152152000, 4260256000, 132067936000, 4490309824000, 166141463488000, 6645658539520000, 285763317199360000, 13145112591170560000, 644110516967357440000, 33493746882302586880000, 1842156078526642278400000
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OFFSET
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0,2
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COMMENTS
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Related to A007559(n+1) ((3*n+1)!!! triple factorials).
Row m=4 of the array A(4; m,n) := ((3*n+m)(!^3))/m(!^3), m >= 0, n >= 0.
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LINKS
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FORMULA
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a(n) = ((3*n+4)(!^3))/4(!^3).
E.g.f.: 1/(1-3*x)^(7/3).
Sum_{n>=0} 1/a(n) = 1 + 3*(3*e)^(1/3)*(Gamma(7/3) - Gamma(7/3, 1/3)). - Amiram Eldar, Dec 23 2022
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MATHEMATICA
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With[{nn = 30}, CoefficientList[Series[1/(1-3*x)^(7/3), {x, 0, nn}], x]* Range[0, nn]! ] (* G. C. Greubel, Aug 15 2018 *)
With[{c=Times@@Range[4, 1, -3]}, Table[(Times@@Range[3n+4, 1, -3])/c, {n, 0, 20}]] (* Harvey P. Dale, Feb 06 2023 *)
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PROG
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(PARI) x='x+O('x^30); Vec(serlaplace(1/(1-3*x)^(7/3))) \\ G. C. Greubel, Aug 15 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(1/(1-3*x)^(7/3))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Aug 15 2018
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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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STATUS
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approved
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