OFFSET
1,1
COMMENTS
Column 1 of A231324.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) + 12*a(n-2) - 8*a(n-3).
Conjectures from Colin Barker, Mar 18 2018: (Start)
G.f.: 6*x*(1 - 2*x) / ((1 + 2*x)*(1 - 8*x + 4*x^2)).
a(n) = ((-2)^(1+n) + (4-2*sqrt(3))^n + (2*(2+sqrt(3)))^n) / 2.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..1....0..1....0..0....0..1....0..1....0..0....0..1....0..1....0..0
..1..1....2..2....0..2....1..1....2..2....2..2....1..2....0..2....2..1....1..2
..2..1....1..2....0..0....0..0....0..2....0..1....0..1....1..2....2..1....0..1
..2..2....1..0....1..1....1..0....0..1....2..0....0..1....2..1....1..2....0..2
..1..0....1..2....2..0....1..2....0..2....1..1....0..1....0..0....1..0....1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 07 2013
STATUS
approved