A224452 The Wiener index of the nanostar dendrimer NS_2[n], defined pictorially in the A. R. Ashrafi et al. reference.

198, 2646, 21558, 141686, 825078, 4438006, 22578678, 110311926, 522899958, 2422104566, 11019370998, 49421451766, 219106574838, 962208334326, 4192177750518, 18142557897206, 78066631049718, 334254292599286, 1424972878709238

Offset

0,1

Comments

a(2) and a(3) have been checked by the direct computation of the Wiener index (using Maple).

References

A. R. Ashrafi and P. Nikzad, Kekulé index and bounds of energy for nanostar dendrimers, Digest J. of Nanomaterials and Biostructures, 4, No. 2, 2009, 383-388.

Links

Table of n, a(n) for n=0..18.

Formula

a(n) = 502 + 1280n*4^n + 1120n*2^n + 2000*2^n - 2304*4^n.

G.f.: 2(99 + 36z - 84z^2 + 736z^3 + 1472z^4)/((1-z)(1-2z)^2*(1-4z)^2).

Maple

a:= proc(n) options operator, arrow: 502+1280*4^n*n+1120*2^n*n+2000*2^n-2304*4^n end proc: seq(a(n), n = 0 .. 18);

Crossrefs

Cf. A224453.

Sequence in context: A159204 A075457 A364860 * A227705 A331098 A290933

Adjacent sequences: A224449 A224450 A224451 * A224453 A224454 A224455

Keyword

nonn,easy

Author

Emeric Deutsch, Apr 06 2013

Status

approved