OFFSET
1,1
REFERENCES
M. V. Diudea, I. Gutman, J. Lorentz, Molecular Topology, Nova Science Publishers, Huntington, NY (2001).
LINKS
I. Gutman, S. Klavzar, An algorithm for the calculation of the Szeged index of benzenoid hydrocarbons, preprint.
I. Gutman, S. Klavzar, An algorithm for the calculation of the Szeged index of benzenoid hydrocarbons, J. Chem. Inf. Comput. Sci., 35, 1995, 1011-1014.
I. Gutman, P. V. Khadikar, T. Khaddar, Wiener and Szeged indices of benzenoid hydrocarbons containing a linear polyacene fragment, Commun. Math. Chem. (MATCH), 35, 1997, 105-116.
FORMULA
a(k) = (12k^6+72k^5+137k^92k^3+13k^2-2k)/6.
G.f: 2z(27+315z+367z^2+13z^3-2z^4)/(1-z)^7.
EXAMPLE
a(1)=54; indeed, the benzenoid consists of 1 hexagon and each of its six edges contributes 3*3 towards the Szeged index; 6*9 = 54.
MAPLE
a := proc (n) options operator, arrow: 2*n^6+12*n^5+(137/6)*n^4+(46/3)*n^3+(13/6)*n^2-(1/3)*n end proc: seq(a(n), n = 1 .. 30);
CROSSREFS
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Aug 07 2014
STATUS
approved