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A106805
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Expansion of g.f.: 1/(1 - 2*x - x^2 + x^3).
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1
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1, 2, 5, 11, 25, 56, 126, 283, 636, 1429, 3211, 7215, 16212, 36428, 81853, 183922, 413269, 928607, 2086561, 4688460, 10534874, 23671647, 53189708, 119516189, 268550439, 603427359, 1355888968, 3046654856, 6845771321, 15382308530, 34563733525, 77664004259
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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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G.f. for sequence with 1 prepended: 1/( 1 - Sum_{k>=0} x*(x+x^2-x^3)^k ) ). - Joerg Arndt, Sep 30 2012
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MATHEMATICA
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PROG
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(PARI) Vec( 1/(1-2*x-x^2+x^3) + O(x^66) ) /* Joerg Arndt, Sep 30 2012 */
(Magma) I:=[1, 2, 5]; [n le 3 select I[n] else 2*Self(n-1) +Self(n-2) -Self(n-3): n in [1..36]]; // G. C. Greubel, Sep 11 2021
(Sage)
P.<x> = PowerSeriesRing(ZZ, prec)
return P( 1/(1-2*x-x^2+x^3) ).list()
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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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EXTENSIONS
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Edited by the Associate Editors of the OEIS, Apr 09 2009
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STATUS
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approved
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