OFFSET
0,1
COMMENTS
a(0) has been checked by the direct computation of the Wiener index (using Maple).
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
N. E. Arif, Roslan Hasni and Saeid Alikhani, Fourth order and fourth sum connectivity indices of polyphenylene dendrimers, J. Applied Science, 12 (21), 2012, 2279-2282.
Index entries for linear recurrences with constant coefficients, signature (19,-150,636,-1560,2208,-1664,512).
FORMULA
a(n) = 407284 + (-2453054 + 211431*n - 103545*n^2)*2^n + (2049492 - 1303920*n + 608400*n^2)*4^n.
G.f.: 2*(1861 + 531059*x - 165878*x^2 - 7414660*x^3 + 13296352*x^4 - 4263232*x^5 + 3512832*x^6)/((1 - x)(1 - 2*x)^3*(1 - 4*x)^3).
a(n) = 19*a(n-1) - 150*a(n-2) + 636*a(n-3) - 1560*a(n-4) + 2208*a(n-5) - 1664*a(n-6) + 512*a(n-7) for n>6. - Colin Barker, May 30 2018
MAPLE
a := proc (n) options operator, arrow: 407284-2453054*2^n-1303920*4^n*n+211431*2^n*n+608400*4^n*n^2-103545*2^n*n^2+2049492*4^n end proc: seq(a(n), n = 0 .. 18);
PROG
(PARI) Vec(2*(1861 + 531059*x - 165878*x^2 - 7414660*x^3 + 13296352*x^4 - 4263232*x^5 + 3512832*x^6) / ((1 - x)*(1 - 2*x)^3*(1 - 4*x)^3) + O(x^20)) \\ Colin Barker, May 30 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Apr 06 2013
STATUS
approved