OFFSET
1,1
COMMENTS
Column 2 of A217964.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..179
FORMULA
Empirical: a(n) = 4*a(n-1) + 2*a(n-2) - a(n-4).
Empirical g.f.: x*(1 + x)*(3 + 2*x + x^2) / (1 - 4*x - 2*x^2 + x^4). - Colin Barker, Jul 23 2018
EXAMPLE
Some solutions for n=3:
..0..0....0..0....2..2....1..0....2..1....1..1....2..2....2..1....2..2....0..0
..0..0....1..2....2..2....0..0....1..0....2..2....2..2....1..1....1..0....0..2
..0..2....1..1....0..0....0..2....0..0....1..1....2..2....0..0....0..0....2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 16 2012
STATUS
approved