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 (see p. 167, Table 10.5/I/6).
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
FORMULA
a(n-2) = (n^7-n^3)/(2^7-2^3). - David Radcliffe, Dec 27 2008
G.f.: (1+10*x+20*x^2+10*x^3+x^4)/(1-x)^8. - Colin Barker, Feb 09 2012
MAPLE
a:=n->(n+1)*(n+2)^3*(n+3)*(n^2+4*n+5)/120: seq(a(n), n=0..33);
PROG
(PARI) a(n)=n-=2; (n^7-n^3)/120 \\ Charles R Greathouse IV, Feb 09 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Nov 18 2005
STATUS
approved