OFFSET
0,2
COMMENTS
Kekulé numbers for certain benzenoids.
REFERENCES
S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 229).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1)
FORMULA
G.f.: ( -1-6*x-3*x^2 ) / (x-1)^7 . - R. J. Mathar, Feb 16 2011
MAPLE
a:=n->(1/360)*(n+1)*(n+2)*(n+3)*(n+4)*(5*n^2+19*n+15): seq(a(n), n=0..36);
MATHEMATICA
LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {1, 13, 73, 273, 798, 1974, 4326}, 40] (* Vincenzo Librandi, Apr 23 2017 *)
PROG
(PARI) a(n)=(n+1)*(n+2)*(n+3)*(n+4)*(5*n^2+19*n+15)/360 \\ Charles R Greathouse IV, Oct 16 2015
(Magma) [(n+1)*(n+2)*(n+3)*(n+4)*(5*n^2+19*n+15)/360: n in [0..30]]; // Vincenzo Librandi, Apr 23 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jun 12 2005
STATUS
approved