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A021134
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Expansion of 1/((1-x)(1-2x)(1-5x)(1-9x)).
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1
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1, 17, 200, 2050, 19731, 184047, 1688890, 15362600, 139076861, 1255760077, 11322184380, 102001381950, 918521058391, 8269232646107, 74435809450670, 669985863300100, 6030190661052321, 54273305406490137
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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)=17; for n>1, a(n) = 14*a(n-1) -45*a(n-2) +2^n -1. - Vincenzo Librandi, Jul 07 2013
a(0)=1, a(1)=17, a(2)=200, a(3)=2050; for n>3, a(n) = 17*a(n-1) -89*a(n-2) +163*a(n-3) -90*a(n-4). - Vincenzo Librandi, Jul 07 2013
a(n) = (3*9^(n+3) - 14*5^(n+3) +32*2^(n+3) - 21)/672. [Yahia Kahloune, Jul 07 2013]
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MATHEMATICA
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CoefficientList[Series[1 / ((1 - x) (1 - 2 x) (1 - 5 x) (1 - 9 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 07 2013 *)
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PROG
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(Magma) m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-2*x)*(1-5*x)*(1-9*x)))); /* or */ I:=[1, 17, 200, 2050]; [n le 4 select I[n] else 17*Self(n-1)-89*Self(n-2)+163*Self(n-3)-90*Self(n-4): n in [1..25]]; // Vincenzo Librandi, Jul 07 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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