OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
Everett Sullivan, Linear chord diagrams with long chords, arXiv preprint arXiv:1611.02771 [math.CO], 2016.
Index entries for linear recurrences with constant coefficients, signature (3).
FORMULA
G.f.: (5*x^3+9*x^2+9*x-15)*x/(3*x-1). - Alois P. Heinz, Oct 17 2017
From Colin Barker, Oct 18 2017: (Start)
a(n) = 292*3^(n-4) for n>3.
a(n) = 3*a(n-1) for n>4.
(End)
MATHEMATICA
Join[{15, 36, 99}, NestList[3#&, 292, 30]] (* Harvey P. Dale, Sep 25 2018 *)
PROG
(PARI) Vec(x*(15 - 9*x - 9*x^2 - 5*x^3) / (1 - 3*x) + O(x^30)) \\ Colin Barker, Oct 18 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Oct 10 2017
EXTENSIONS
More terms from Alois P. Heinz, Oct 17 2017
STATUS
approved