

A143938


The Wiener index of a benzenoid consisting of a linear chain of n hexagons.


14



27, 109, 279, 569, 1011, 1637, 2479, 3569, 4939, 6621, 8647, 11049, 13859, 17109, 20831, 25057, 29819, 35149, 41079, 47641, 54867, 62789, 71439, 80849, 91051, 102077, 113959, 126729, 140419, 155061, 170687, 187329, 205019, 223789, 243671
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OFFSET

1,1


REFERENCES

A. A. Dobrynin, I. Gutman, S. Klavzar, and P. Zigert, Wiener index of hexagonal systems, Acta Applicandae Mathematicae, 72, 247294, 2002.


LINKS

Table of n, a(n) for n=1..35.


FORMULA

a(n) = (1/3)*(16*n^3 + 36*n^2 + 26*n + 3).
G.f.: z*(27+z+5*z^2z^3)/(1z)^4.
a(n) = Sum(k*A143937(n,k), k=1..2*n+1).


EXAMPLE

a(1)=27 because in a hexagon we have 6 distances equal to 1, 6 distances equal to 2 and 3 distances equal to 3 (6*1+6*2+3*3=27).


MAPLE

seq((16*n^3+36*n^2+26*n+3)*1/3, n = 1 .. 35)


CROSSREFS

A143937
Sequence in context: A193391 A193399 A193393 * A042428 A158554 A029699
Adjacent sequences: A143935 A143936 A143937 * A143939 A143940 A143941


KEYWORD

nonn


AUTHOR

Emeric Deutsch, Sep 06 2008


STATUS

approved



