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A134068
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a(n) = 2*a(n-2) + 4*a(n-3), with initial terms 0, 3, 3.
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1
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0, 3, 3, 6, 18, 24, 60, 120, 216, 480, 912, 1824, 3744, 7296, 14784, 29568, 58752, 118272, 235776, 471552, 944640, 1886208, 3775488, 7550976, 15095808, 30203904, 60395520, 120791040, 241606656, 483164160, 966377472, 1932754944, 3865411584, 7731019776, 15461842944
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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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G.f.: 3*x*(1 + x)/((1 - 2*x)*(1 + 2*x + 2*x^2)).
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PROG
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(PARI) concat([0], Vec(3*(1 + x)/((1 - 2*x)*(1 + 2*x + 2*x^2)) + O(x^40))) \\ Andrew Howroyd, Jan 03 2020
(Magma) a:=[0, 3, 3]; [n le 3 select a[n] else 2*Self(n-2) + 4*Self(n-3):n in [1..35]]; // Marius A. Burtea, Jan 03 2020
(Magma) R<x>:=PowerSeriesRing(Integers(), 35); [0] cat Coefficients(R!( 3*x*(1 + x)/((1 - 2*x)*(1 + 2*x + 2*x^2)))); // Marius A. Burtea, Jan 03 2020
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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a(12) corrected and terms a(13) and beyond from Andrew Howroyd, Jan 03 2020
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STATUS
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approved
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