OFFSET
1,1
COMMENTS
Column 2 of A205823.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - a(n-2) - 4*a(n-3) + 2*a(n-4).
Empirical g.f.: 6*x*(11 - 8*x - 14*x^2 + 9*x^3) / ((1 - x)*(1 + x)*(1 - 4*x + 2*x^2)). - Colin Barker, Jun 12 2018
EXAMPLE
Some solutions for n=4:
..2..0..0....1..2..2....2..0..0....1..1..1....2..1..2....1..0..1....0..0..2
..2..1..2....0..0..1....2..1..2....2..0..2....0..1..0....2..0..2....2..1..1
..2..0..2....1..2..1....2..0..2....2..1..1....2..1..2....1..0..1....2..0..2
..2..1..1....0..0..0....1..0..1....2..0..2....0..1..0....1..2..1....1..0..1
..2..0..2....2..1..2....1..2..1....1..1..2....0..2..2....0..2..0....1..2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 01 2012
STATUS
approved