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A127896
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Expansion of 1/(1 + 2*x + 3*x^2 + x^3).
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7
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1, -2, 1, 3, -7, 4, 10, -25, 16, 33, -89, 63, 108, -316, 245, 350, -1119, 943, 1121, -3952, 3598, 3539, -13920, 13625, 10971, -48897, 51256, 33208, -171287, 191694, 97265, -598325, 713161, 271388, -2083934
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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a(n) = Sum_{k=0..n} (-1)^(n-k)*C(n+2k+2,n-k).
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MATHEMATICA
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CoefficientList[Series[1/(1+2x+3x^2+x^3), {x, 0, 40}], x] (* Harvey P. Dale, Apr 19 2011 *)
LinearRecurrence[{-2, -3, -1}, {1, -2, 1}, 30] (* G. C. Greubel, Apr 29 2018 *)
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PROG
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(PARI) x='x+O('x^50); Vec(1/(1+2*x+3*x^2+x^3)) \\ G. C. Greubel, Apr 29 2018
(Magma) I:=[1, -2, 1]; [n le 3 select I[n] else -2*Self(n-1) -3*Self(n-2) -Self(n-3): n in [1..50]]; // G. C. Greubel, Apr 29 2018
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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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