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 A206278 Total number of triangles in Cayley graph Cay(Z_{2^n}, QR*(2^n)). 1
 0, 0, 128, 1024, 6656, 53248, 387072, 3096576, 24092672, 192741376, 1530822656, 12246581248, 97793998848, 782351990784, 6255953838080, 50047630704640, 400335237545984, 3202681900367872, 25620722214764544, 204965777718116352, 1639714493699194880, 13117715949593559040, 104941539947077173248, 839532319576617385984 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,3 LINKS Vincenzo Librandi, Table of n, a(n) for n = 3..1000 Reinaldo E. Giudici and Aurora A. Olivieri, Quadratic modulo 2n Cayley graphs, Discrete Math. 215 (2000), no. 1-3, 73-79. See T(n) in Theorem 3.1. Index entries for linear recurrences with constant coefficients, signature (8,20,-160,-64,512). FORMULA G.f.: 128*x^5*(32*x^2-1) / ((2*x-1)*(2*x+1)*(4*x-1)*(4*x+1)*(8*x-1)). - Colin Barker, Jul 23 2013 MAPLE f:=n-> if n mod 2 = 1 then (1/45)*(2^(3*(n-1))+5*2^(2*n-1)-7*2^(n+2)); else (1/45)*(2^(3*(n-1))+5*2^(2*n)-7*2^(n+4)); fi; [seq(f(n), n=3..40)]; MATHEMATICA CoefficientList[Series[128 x^2 (32 x^2 - 1) / ((2 x - 1) (2 x + 1) (4 x - 1) (4 x + 1) (8 x - 1)), {x, 0, 33}], x] (* Vincenzo Librandi, Aug 21 2016 *) LinearRecurrence[{8, 20, -160, -64, 512}, {0, 0, 128, 1024, 6656}, 30] (* Harvey P. Dale, May 31 2019 *) CROSSREFS Sequence in context: A183972 A143708 A130813 * A100628 A344303 A221599 Adjacent sequences: A206275 A206276 A206277 * A206279 A206280 A206281 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Feb 05 2012 STATUS approved

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Last modified November 27 06:39 EST 2022. Contains 358362 sequences. (Running on oeis4.)