OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-3) + 4*a(n-6) for n>9.
Empirical g.f.: 2*x*(28 + 44*x + 69*x^2 + 32*x^3 + 68*x^4 + 78*x^5 + 4*x^6 - 8*x^7 - 4*x^8) / (1 - 2*x^3 - 4*x^6). - Colin Barker, Oct 16 2018
EXAMPLE
Some solutions for n=5:
..0..2..1....0..1..2....1..2..0....0..1..2....1..2..0....0..2..1....2..0..2
..2..1..2....1..2..1....2..0..1....1..2..0....2..0..2....2..1..2....1..2..1
..1..2..0....2..0..2....0..1..0....2..1..2....1..2..1....1..2..0....2..0..2
..2..0..1....1..2..0....1..0..2....0..2..1....2..0..2....2..0..2....1..2..0
..0..1..0....2..1..2....0..2..1....1..0..2....1..2..0....1..2..1....2..1..2
..1..0..2....0..2..1....2..1..2....0..1..0....2..1..2....2..0..2....1..2..0
..0..2..0....1..0..2....0..2..1....1..0..2....0..2..1....1..2..0....0..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 01 2014
STATUS
approved