OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) - 6*a(n-2).
Conjectures from Colin Barker, Oct 19 2018: (Start)
G.f.: 3*x*(7 - 18*x) / ((1 - 2*x)*(1 - 3*x)).
a(n) = 3*(2^(1+n) + 3^n).
(End)
EXAMPLE
Some solutions for n=5:
..0..1....2..2....0..1....1..1....0..0....2..2....1..1....2..2....2..2....1..1
..0..1....2..2....1..0....2..2....1..1....0..0....0..0....1..1....2..2....2..2
..0..1....1..1....1..0....0..0....1..1....2..2....2..2....0..0....0..0....2..2
..1..0....0..0....1..0....0..0....1..1....1..1....0..0....1..1....1..1....0..0
..0..1....2..2....1..0....2..2....2..2....2..2....1..1....0..0....1..1....2..2
..0..1....0..0....0..1....0..0....1..1....1..1....2..2....0..0....1..1....2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2014
STATUS
approved