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A084056
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a(n) = -a(n-1) + a(n-2) + a(n-3), with a(0)=0, a(1)=1, a(2)=-3.
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4
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0, 1, -3, 4, -6, 7, -9, 10, -12, 13, -15, 16, -18, 19, -21, 22, -24, 25, -27, 28, -30, 31, -33, 34, -36, 37, -39, 40, -42, 43, -45, 46, -48, 49, -51, 52, -54, 55, -57, 58, -60, 61, -63, 64, -66, 67, -69, 70, -72, 73, -75, 76, -78, 79, -81, 82, -84, 85, -87, 88, -90
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = (1/4) * ((1-6*n) * (-1)^n - 1).
G.f.: (x-2*x^2)/((1+x)*(1-x^2)).
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MAPLE
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MATHEMATICA
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LinearRecurrence[{-1, 1, 1}, {0, 1, -3}, 101] (* T. D. Noe, Nov 11 2013 *)
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PROG
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(Magma) [((1-6*n)*(-1)^n-1)/4 : n in [0..100]]; // Zaki Khandaker, Jun 21 2015
(PARI) concat(0, Vec(x*(2*x-1)/((x-1)*(x+1)^2) + O(x^100))) \\ Colin Barker, Jun 21 2015
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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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EXTENSIONS
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STATUS
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approved
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