OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 12*a(n-1) + 20*a(n-2) + 9*a(n-3).
Empirical g.f.: x*(7 + 13*x + 9*x^2) / (1 - 12*x - 20*x^2 - 9*x^3). - Colin Barker, Oct 04 2018
EXAMPLE
Some solutions for n=4:
..1..2..0....1..2..2....1..2..2....0..1..0....0..1..0....2..1..2....2..2..2
..1..1..2....2..1..2....2..1..0....2..2..2....2..2..1....2..1..2....0..1..0
..0..1..1....0..2..2....2..1..0....0..1..0....0..1..2....2..2..2....0..2..0
..1..2..1....2..1..2....2..2..1....0..1..2....0..2..1....1..2..2....2..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 22 2013
STATUS
approved