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A114285
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Expansion of g.f. (1 - 3*x)/((1 - x)*(1 - x^2)).
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5
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1, -2, -1, -4, -3, -6, -5, -8, -7, -10, -9, -12, -11, -14, -13, -16, -15, -18, -17, -20, -19, -22, -21, -24, -23, -26, -25, -28, -27, -30, -29, -32, -31, -34, -33, -36, -35, -38, -37, -40, -39, -42, -41, -44, -43, -46, -45, -48, -47, -50, -49, -52, -51, -54, -53, -56, -55, -58, -57, -60, -59, -62, -61
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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..floor(n/2)} 3*0^(n-2k) - 2.
a(n) = 3*(1 + (-1)^n)/2 - 2*floor((n+2)/2).
a(n) = a(n-1) + a(n-2) - a(n-3), n > 2.
a(n) = (-1)^n - n. (End)
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MAPLE
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MATHEMATICA
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CoefficientList[Series[(1 - 3 x)/((1 - x) (1 - x^2)), {x, 0, 70}] , x] (* Vincenzo Librandi, Sep 07 2015 *)
LinearRecurrence[{1, 1, -1}, {1, -2, -1}, 70] (* Harvey P. Dale, Jul 24 2019 *)
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PROG
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(Magma) I:=[1, -2, -1]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..70]]; // Vincenzo Librandi, Sep 07 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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STATUS
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approved
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