OFFSET
0,3
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
M. Diepenbroek, M. Maus and A. Stoll, Pattern Avoidance in Reverse Double Lists, Preprint 2015. See Table 3.
Index entries for linear recurrences with constant coefficients, signature (2,1).
FORMULA
From Colin Barker, Apr 12 2016: (Start)
a(n) = ((1+sqrt(2))^n*(-5+4*sqrt(2)) + (1-sqrt(2))^n*(5+4*sqrt(2)))/sqrt(2) for n>2.
a(n) = 2*a(n-1)+a(n-2) for n>4.
(End)
MATHEMATICA
Join[{0, 1, 2}, LinearRecurrence[{2, 1}, {6, 16}, 30]] (* Jean-François Alcover, Nov 02 2021 *)
PROG
(PARI) concat(0, Vec(x*(1+x)*(1-x+2*x^2)/(1-2*x-x^2) + O(x^50))) \\ Colin Barker, Apr 12 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Apr 06 2016
STATUS
approved