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 A131358 a(3*k) = 0, a(3*k+1) = k+1, a(3*k+2) = -k. 0
 0, 1, 0, 0, 2, -1, 0, 3, -2, 0, 4, -3, 0, 5, -4, 0, 6, -5, 0, 7, -6, 0, 8, -7, 0, 9, -8, 0, 10, -9, 0, 11, -10, 0, 12, -11, 0, 13, -12, 0, 14, -13, 0, 15, -14, 0, 16, -15, 0, 17, -16, 0, 18, -17, 0, 19, -18, 0, 20, -19, 0, 21, -20, 0, 22, -21, 0, 23, -22, 0, 24, -23, 0, 25, -24, 0, 26, -25, 0, 27, -26, 0, 28, -27, 0, 29, -28, 0, 30, -29 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS Index entries for linear recurrences with constant coefficients, signature (-1,-1,1,1,1). FORMULA a(n) = 4*(-1)^floor(2*n/3)*sin(n*Pi/3)*(n*sin(n*Pi/3) - sqrt(3)*cos(n*Pi))/9. - Wesley Ivan Hurt, Sep 24 2017 G.f.: x*(1 + x)*(1 + x^2)/((1 - x)*(1 + x + x^2)^2). - Bruno Berselli, Sep 28 2017 CROSSREFS Sequence in context: A157497 A257961 A225310 * A291895 A177351 A117901 Adjacent sequences: A131355 A131356 A131357 * A131359 A131360 A131361 KEYWORD sign,easy AUTHOR Paul Curtz, Sep 30 2007 STATUS approved

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Last modified February 3 13:54 EST 2023. Contains 360035 sequences. (Running on oeis4.)