OFFSET
0,1
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. 310).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
FORMULA
G.f.: 4(5 + 73x + 105x^2 + x^3 - 4x^4)/(1-x)^7.
From Amiram Eldar, May 31 2022: (Start)
Sum_{n>=0} 1/a(n) = 8473/6912 - 43*Pi^2/288 + zeta(3)/4.
Sum_{n>=0} (-1)^n/a(n) = 16*log(2)/9 + 3*zeta(3)/16 - 11*Pi^2/576 - 8441/6912. (End)
MAPLE
a:=n->(n+1)^3*(n+2)^2*(n+5): seq(a(n), n=0..30);
MATHEMATICA
Table[(n+1)^3 (n+2)^2 (n+5), {n, 0, 30}] (* Harvey P. Dale, Sep 24 2011 *)
PROG
(Magma) [(n+1)^3*(n+2)^2*(n+5): n in [0..30]]; // Vincenzo Librandi, Sep 25 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jun 19 2005
STATUS
approved