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A038989
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Expansion of (1 - x^2 - 2*x^3) / (1 - 2*x - 2*x^2 - 2*x^3 + x^4).
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1
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1, 2, 5, 14, 41, 118, 341, 986, 2849, 8234, 23797, 68774, 198761, 574430, 1660133, 4797874, 13866113, 40073810, 115815461, 334712894, 967338217, 2795659334, 8079605429, 23350493066, 67484177441, 195032892538, 563655520661, 1628994688214, 4707882025385
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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(n) = 2*a(n-1) + 2*a(n-2) + 2*a(n-3) - a(n-4) for n>3. - Colin Barker, Jul 16 2017
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MAPLE
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seq(coeff(series((1-x^2-2*x^3)/(1-2*x-2*x^2-2*x^3+x^4), x, n+1), x, n), n = 0 .. 30); # Muniru A Asiru, Sep 12 2018
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PROG
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(PARI) Vec((1 - x^2 - 2*x^3) / (1 - 2*x - 2*x^2 - 2*x^3 + x^4) + O(x^30)) \\ Colin Barker, Jul 16 2017
(GAP) a:=[1, 2, 5, 14];; for n in [5..30] do a[n]:=2*a[n-1]+2*a[n-2]+2*a[n-3]-a[n-4]; od; a; # Muniru A Asiru, Sep 12 2018
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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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