OFFSET
1,1
COMMENTS
a(n) = number of edges of the dendrimer nanostar NS2[n], defined pictorially in Fig. 2 of the Madanshekaf reference.
REFERENCES
A. Madanshekaf, The Randic index of some dendrimer nanostars, J. Appl. Math. & Informatics, 29, No. 5-6, 2011, 1075-1080.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (3,-2).
FORMULA
From Colin Barker, May 15 2018: (Start)
G.f.: 6*x*(16 - 9*x) / ((1 - x)*(1 - 2*x)).
a(n) = 3*a(n-1) - 2*a(n-2) for n>2.
(End)
MAPLE
seq(69*2^n-42, n = 1 .. 40);
MATHEMATICA
Array[69*2^# - 42 &, 33] (* Michael De Vlieger, May 14 2018 *)
PROG
(GAP) List([1..40], n->69*2^n-42); # Muniru A Asiru, May 15 2018
(PARI) Vec(6*x*(16 - 9*x) / ((1 - x)*(1 - 2*x)) + O(x^40)) \\ Colin Barker, May 15 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, May 14 2018
STATUS
approved