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A019664
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Expansion of 1/((1-4x)(1-8x)(1-9x)).
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1
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1, 21, 301, 3669, 40957, 433125, 4418317, 43942773, 428973853, 4128937989, 39306876973, 370937567637, 3475860284989, 32382187083813, 300235508341069, 2772487245505461, 25515330868003165, 234141560259529797
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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(n) = 4^(n+1)/5+9^(n+2)/5-2*8^(n+1). - R. J. Mathar, Nov 11 2012
a(0)=1, a(1)=21, a(2)=301; for n>2, a(n) = 21*a(n-1) -140*a(n-2) +288*a(n-3). - Vincenzo Librandi, Jul 03 2013
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MATHEMATICA
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CoefficientList[Series[1 / ((1 - 4 x) (1 - 8 x) (1 - 9 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 03 2013 *)
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PROG
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(Magma) m:=20; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-4*x)*(1-8*x)*(1-9*x)))); /* or */ I:=[1, 21, 301]; [n le 3 select I[n] else 21*Self(n-1)-140*Self(n-2)+288*Self(n-3): n in [1..20]]; // Vincenzo Librandi, Jul 03 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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