OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 4*a(n-3).
Conjectures from Colin Barker, Jan 11 2019: (Start)
G.f.: x*(1 - x - x^2) / ((1 - 2*x)*(1 - 2*x - 2*x^2)).
a(n) = (-3*2^n + (3-2*sqrt(3))*(1-sqrt(3))^n + (1+sqrt(3))^n*(3+2*sqrt(3))) / 12.
(End)
EXAMPLE
Some solutions for n=4:
..0..2..2..1....0..2..1..0....0..0..1..2....0..0..2..2....0..0..2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 26 2016
STATUS
approved