OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3).
Conjectures from Colin Barker, Oct 19 2018: (Start)
G.f.: 3*x*(43 - 181*x + 162*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).
a(n) = 3*(12 + 7*2^(1+n) + 3^n).
(End)
EXAMPLE
Some solutions for n=5:
..2..0..0..2....0..0..0..0....2..2..2..2....0..1..0..0....1..1..1..1
..2..0..0..2....0..0..0..0....1..1..1..1....0..1..0..0....1..1..1..1
..2..0..0..2....0..0..0..0....1..1..1..1....1..0..1..1....0..0..0..0
..2..0..0..2....2..2..2..2....0..0..0..0....0..1..0..0....0..0..0..0
..0..2..2..0....1..1..1..1....2..2..2..2....0..1..0..0....2..2..2..2
..2..0..0..2....0..0..0..0....1..1..1..1....0..1..0..0....0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2014
STATUS
approved