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A038390 Bisection of A028289. 1
1, 2, 5, 11, 17, 27, 42, 57, 78, 106, 134, 170, 215, 260, 315, 381, 447, 525, 616, 707, 812, 932, 1052, 1188, 1341, 1494, 1665, 1855, 2045, 2255, 2486, 2717, 2970, 3246, 3522, 3822, 4147, 4472, 4823, 5201, 5579, 5985, 6420, 6855, 7320, 7816, 8312, 8840, 9401 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

B. N. Cyvin et al., Enumeration of conjugated hydrocarbons: Hollow hexagons revisited, Structural Chem., 6 (1995), 85-88, equation (7).

Index entries for linear recurrences with constant coefficients, signature (2,-1,2,-4,2,-1,2,-1).

FORMULA

G.f.: (x^3+2*x^2+1) / ((x-1)^4*(x^2+x+1)^2). - Colin Barker, Aug 30 2013

a(n) = (2*n^2+2+floor(n/3)*(10*floor(n/3)^2-(8*n-15)*floor(n/3)+2*n^2-8*n+7))/2. - Luce ETIENNE, Sep 14 2015

MATHEMATICA

CoefficientList[Series[(x^3 + 2 x^2 + 1)/((x - 1)^4 (x^2 + x + 1)^2), {x, 0, 50}], x] (* Vincenzo Librandi, Oct 22 2013 *)

CROSSREFS

Sequence in context: A228344 A157421 A274830 * A048210 A153222 A023222

Adjacent sequences:  A038387 A038388 A038389 * A038391 A038392 A038393

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Colin Barker, Aug 30 2013

STATUS

approved

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Last modified October 16 23:30 EDT 2019. Contains 328103 sequences. (Running on oeis4.)