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 A187307 Hankel transform of an alternating sum of Motzkin numbers. 1
 1, 2, 2, -1, -5, -5, 1, 8, 8, -1, -11, -11, 1, 14, 14, -1, -17, -17, 1, 20, 20, -1, -23, -23, 1, 26, 26, -1, -29, -29, 1, 32, 32, -1, -35, -35, 1, 38, 38, -1, -41, -41, 1, 44, 44, -1, -47, -47, 1, 50, 50, -1, -53, -53, 1, 56, 56, -1, -59, -59, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Hankel transform of A187306. LINKS Index entries for linear recurrences with constant coefficients, signature (2,-3,2,-1) FORMULA G.f.: (1+x^2-x^3)/(1-x+x^2)^2. a(n) = (1/3)*(2*n+2-(n-1)*cos(2*n*Pi/3)-(n-1)*cos(4*n*Pi/3)-cos((2*n+1)*Pi/3)-sin((8*n+1)*Pi/6))*(-1)^floor(n/3). - Wesley Ivan Hurt, Sep 25 2017 PROG (PARI) Vec((1+x^2-x^3)/(1-x+x^2)^2 + O(x^80)) \\ Michel Marcus, Sep 26 2017 CROSSREFS Cf. A187306. Sequence in context: A158068 A210879 A176265 * A280785 A204851 A114292 Adjacent sequences:  A187304 A187305 A187306 * A187308 A187309 A187310 KEYWORD sign,easy AUTHOR Paul Barry, Mar 08 2011 STATUS approved

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Last modified October 22 13:20 EDT 2017. Contains 293774 sequences.