OFFSET
0,1
COMMENTS
a(n) is the number of vertices in the N-branched phenylacetylene NSB[n], shown pictorially in the Yarahmadi reference (for n=2).
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Z. Yarahmadi and G. H. Fath-Tabar, The Wiener, Szeged, PI, Vertex PI, the first and second Zagreb indices of N-branched phenylacetylenes dendrimers, MATCH: Commun. Math. Comput. Chem, 65 (2011) 201-208.
Index entries for linear recurrences with constant coefficients, signature (3,-2).
FORMULA
From Colin Barker, May 10 2018: (Start)
G.f.: (49 - 11*x) / ((1 - x)*(1 - 2*x)).
a(n) = 3*a(n-1) - 2*a(n-2) for n>1.
(End)
MAPLE
seq(87*2^n-38, n = 0 .. 35);
PROG
(PARI) Vec((49 - 11*x) / ((1 - x)*(1 - 2*x)) + O(x^30)) \\ Colin Barker, May 10 2018
(GAP) List([0..40], n->87*2^n-38); # Muniru A Asiru, May 10 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, May 10 2018
STATUS
approved