A224461 The Wiener index of Wang's helicene-based dendrimer defined pictorially as DNS_2[n] in the Shabani et al. reference.

1636, 35877, 358267, 2593671, 15836671, 87269679, 449795599, 2213852367, 10541202511, 48969228111, 223231118671, 1002642454863, 4450100228431, 19559951884623, 85281094811983, 369296144564559, 1589885770858831, 6810377914286415, 29044914697011535, 123393405571563855

Offset

1,1

References

H. Shabani, A. R. Ashrafi, I. Gutman, Geometric-arithmetic index: an algebraic approach, Studia UBB, Chemia, LV, 2010, 107-112.

Links

Table of n, a(n) for n=1..20.

Formula

a(n) = 335 + 2^n*(6858*n+37319/2)+4^n*(6561*n-37989/2).

G.f.: x*(1636+14609*x-3430*x^2-9800*x^3)/((1-x)*(1-2*x)^2*(1-4*x)^2).

Maple

a:= proc (n) options operator, arrow: 335+2^n*(6858*n+37319/2)+4^n*(6561*n-37989/2) end proc: seq(a(n), n = 1 .. 20);

Crossrefs

Cf. A224462.

Sequence in context: A072409 A052455 A252619 * A233121 A054808 A218010

Adjacent sequences: A224458 A224459 A224460 * A224462 A224463 A224464

Keyword

nonn,easy

Author

Emeric Deutsch, Jul 12 2013

Status

approved