login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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