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A019793
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Expansion of 1/((1-5x)(1-6x)(1-9x)).
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1
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1, 20, 271, 3110, 32641, 324800, 3125011, 29414090, 272851381, 2506362980, 22871235751, 207773763470, 1881803862121, 17008495407560, 153516126074491, 1384313656687250, 12474986630176861, 112372624930994540
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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) = 25*5^n/4 -12*6^n +27*9^n/4. R. J. Mathar, Jun 29 2013
a(0)=1, a(1)=20, a(2)=271; for n>2, a(n) = 20*a(n-1) -129*a(n-2) +270*a(n-3). - Vincenzo Librandi, Jul 03 2013
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MATHEMATICA
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CoefficientList[Series[1 / ((1 - 5 x) (1 - 6 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/((1-5*x)*(1-6*x)*(1-9*x)))); /* or */ I:=[1, 20, 271]; [n le 3 select I[n] else 20*Self(n-1)-129*Self(n-2)+270*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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