OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-2) + 4*a(n-3).
Empirical g.f.: 4*x^2 / (1 - 2*x + x^2 - 4*x^3). - Colin Barker, Oct 06 2018
EXAMPLE
Some solutions for n=5:
..2..1....0..1....2..1....0..1....2..1....2..1....0..1....0..1....2..1....0..1
..0..2....2..0....0..2....2..2....0..0....0..0....2..1....2..1....0..2....2..1
..1..0....1..2....1..0....1..0....1..2....1..2....0..0....0..1....1..0....0..1
..2..1....0..1....0..1....0..1....0..1....2..1....1..2....2..1....1..2....2..0
..0..2....2..2....2..0....2..2....2..2....0..2....1..0....0..0....1..0....1..2
..1..0....1..0....1..2....1..0....1..0....1..0....1..2....1..2....1..2....1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 02 2013
STATUS
approved