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A176333
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Expansion of (1-3*x)/(1-4*x+9*x^2).
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3
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1, 1, -5, -29, -71, -23, 547, 2395, 4657, -2927, -53621, -188141, -269975, 613369, 4883251, 14012683, 12101473, -77708255, -419746277, -979610813, -140726759, 8253590281, 34280901955, 62841295291, -57162936431, -794223403343
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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a(n) = 3^n*( cos(2n*atan(1/sqrt(5)) - sin(2n*atan(1/sqrt(5))/sqrt(5) ).
a(0)=1, a(1)=1, a(n) = 4*a(n-1) - 9*a(n-2). - Harvey P. Dale, Sep 17 2012
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MAPLE
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seq(coeff(series((1-3*x)/(1-4*x+9*x^2), x, n+1), x, n), n = 0..30); # G. C. Greubel, Dec 07 2019
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MATHEMATICA
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CoefficientList[Series[(1-3x)/(1-4x+9x^2), {x, 0, 30}], x] (* or *) LinearRecurrence[{4, -9}, {1, 1}, 30] (* Harvey P. Dale, Sep 17 2012 *)
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PROG
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(PARI) my(x='x+O('x^30)); Vec((1-3*x)/(1-4*x+9*x^2)) \\ G. C. Greubel, Dec 07 2019
(Magma) I:=[1, 1]; [n le 2 select I[n] else 4*Self(n-1) - 9*Self(n-2): n in [1..30]]; // G. C. Greubel, Dec 07 2019
(Sage)
P.<x> = PowerSeriesRing(ZZ, prec)
return P( (1-3*x)/(1-4*x+9*x^2) ).list()
(GAP) a:=[1, 1];; for n in [3..30] do a[n]:=4*a[n-1]-9*a[n-2]; od; a; # G. C. Greubel, Dec 07 2019
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CROSSREFS
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KEYWORD
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easy,sign
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AUTHOR
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STATUS
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approved
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