OFFSET
1,1
COMMENTS
Column 2 of A209100.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-1) - 4*a(n-2) for n>3.
Conjectures from Colin Barker, Mar 07 2018: (Start)
G.f.: x*(2 - x)*(1 - 2*x) / (1 - 8*x + 4*x^2).
a(n) = ((4-2*sqrt(3))^n*(-1+sqrt(3)) + (1+sqrt(3))*(2*(2+sqrt(3)))^n) / (8*sqrt(3)) for n>1.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..1
..1..2....1..0....1..1....1..1....1..1....1..0....1..1....1..2....2..1....2..1
..2..0....0..1....0..0....2..0....2..2....0..1....2..0....0..2....2..2....2..2
..0..2....0..1....2..0....0..1....1..1....1..2....1..0....2..0....1..2....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 05 2012
STATUS
approved