OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 20*a(n-2) - 8*a(n-3).
Empirical g.f.: 4*x*(12 + 41*x - 18*x^2) / (1 - 2*x - 20*x^2 + 8*x^3). - Colin Barker, Oct 20 2018
EXAMPLE
Some solutions for n=4:
..2..1....0..0....2..0....1..2....0..1....2..0....2..2....2..1....2..2....2..2
..0..0....1..0....1..2....0..2....2..2....1..0....0..2....0..2....2..1....2..1
..0..1....2..0....0..2....1..2....1..0....0..2....1..2....0..1....2..0....1..1
..2..2....2..2....0..0....0..0....2..0....2..2....0..0....2..2....0..0....2..1
..1..2....0..1....1..2....2..1....2..2....0..2....0..1....0..1....1..2....0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2014
STATUS
approved