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A199935 Size (b^3_n) of unit sphere in a certain graph (see Hazama article for precise definition). 1
0, 0, 2, 5, 9, 14, 22, 36, 60, 99, 161, 260, 420, 680, 1102, 1785, 2889, 4674, 7562, 12236, 19800, 32039, 51841, 83880, 135720, 219600, 355322, 574925, 930249, 1505174, 2435422, 3940596, 6376020, 10316619, 16692641, 27009260, 43701900, 70711160, 114413062, 185124225 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,3

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 2..1000

Fumio Hazama, Spectra of graphs attached to the space of melodies, Discr. Math., 311 (2011), 2368-2383. See Table 2.1.

Index entries for linear recurrences with constant coefficients, signature (3,-3,1,1,-1).

FORMULA

a(n) = 2*A130578(n-1) - A130578(n-2).

G.f.: -x^4*(-2+x) / ( (x-1)*(x^2-x+1)*(x^2+x-1) ). - R. J. Mathar, Nov 15 2011

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-4) - a(n-5), with a(2)=0, a(3)=0, a(4)=2, a(5)=5, a(6)=9. - Harvey P. Dale, Jul 04 2013

MATHEMATICA

CoefficientList[Series[-x^2*(-2+x)/((x-1)*(x^2-x+1)*(x^2+x-1)), {x, 0, 50}], x] (* Vincenzo Librandi, Jul 10 2012 *)

LinearRecurrence[{3, -3, 1, 1, -1}, {0, 0, 2, 5, 9}, 40] (* Harvey P. Dale, Jul 04 2013 *)

CROSSREFS

Sequence in context: A306674 A098065 A123690 * A090937 A338666 A325717

Adjacent sequences:  A199932 A199933 A199934 * A199936 A199937 A199938

KEYWORD

nonn,easy,changed

AUTHOR

N. J. A. Sloane, Nov 12 2011

STATUS

approved

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Last modified August 5 00:15 EDT 2021. Contains 346456 sequences. (Running on oeis4.)