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A021484
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Expansion of 1/((1-x)(1-3x)(1-5x)(1-12x)).
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1
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1, 21, 310, 4050, 50371, 613671, 7411240, 89174100, 1071295141, 12861600921, 154369595770, 1852587338550, 22231809806311, 266785528785771, 3201445408153900, 38417440232993400, 461009759536223881
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OFFSET
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0,2
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LINKS
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FORMULA
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a(0)=1, a(1)=21; for n>2, a(n) = 17*a(n-1) -60*a(n-2) +(3^n -1)/2. - Vincenzo Librandi, Jul 10 2013
a(0)=1, a(1)=21, a(2)=310, a(3)=4050; for n>3, a(n) = 21*a(n-1) -131*a(n-2) +291*a(n-3) -180*a(n-4). - Vincenzo Librandi, Jul 10 2013
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MATHEMATICA
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CoefficientList[Series[1 / ((1 - x) (1 - 3 x) (1 - 5 x) (1 - 12 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 10 2013 *)
LinearRecurrence[{21, -131, 291, -180}, {1, 21, 310, 4050}, 30] (* Harvey P. Dale, Sep 20 2016 *)
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PROG
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(Magma) m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-3*x)*(1-5*x)*(1-12*x)))); /* or */ I:=[1, 21, 310, 4050]; [n le 4 select I[n] else 21*Self(n-1)-131*Self(n-2)+291*Self(n-3)-180*Self(n-4): n in [1..25]]; // Vincenzo Librandi, Jul 10 2013
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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