login
A193391
Wiener index of a benzenoid consisting of a spiral chain of n hexagons (s=1; see the Gutman et al. reference).
10
27, 109, 271, 529, 899, 1397, 2039, 2841, 3819, 4989, 6367, 7969, 9811, 11909, 14279, 16937, 19899, 23181, 26799, 30769, 35107, 39829, 44951, 50489, 56459, 62877, 69759, 77121, 84979, 93349, 102247, 111689, 121691, 132269, 143439, 155217, 167619, 180661
OFFSET
1,1
LINKS
A. A. Dobrynin, I. Gutman, S. Klavzar, P. Zigert, Wiener Index of Hexagonal Systems , Acta Applicandae Mathematicae 72 (2002), pp. 247-294.
I. Gutman, S. Klavzar, M. Petkovsek, and P. Zigert, On Hosoya polynomials of benzenoid graphs, Comm. Math. Comp. Chem. (MATCH), 43, 2001, 49-66.
FORMULA
a(n) = (27 - 26*n + 72*n^2 + 8*n^3)/3.
G.f.: x*(27 + x - 3*x^2 - 9*x^3)/(1-x)^4. - Bruno Berselli, Jul 27 2011
PROG
(Magma) [(27 - 26*n + 72*n^2 +8*n^3)/3: n in [1..30]]; // Vincenzo Librandi, Jul 26 2011
(PARI) a(n)=(8*n^3+72*n^2-26*n)/3+9 \\ Charles R Greathouse IV, Jul 26 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jul 25 2011
STATUS
approved