OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 9*a(n-1) - 16*a(n-2) + 11*a(n-3) - 27*a(n-4) + 21*a(n-5) - 4*a(n-6).
Empirical g.f.: x*(1 - x^2 - 4*x^3 - 7*x^4 - 4*x^5) / (1 - 9*x + 16*x^2 - 11*x^3 + 27*x^4 - 21*x^5 + 4*x^6). - Colin Barker, Oct 01 2018
EXAMPLE
Some solutions for n=7:
..0..0....0..0....0..0....0..1....0..0....0..0....0..0....0..0....0..0....0..0
..1..0....2..1....1..2....0..1....1..0....2..1....2..1....0..1....2..1....2..2
..2..2....1..2....1..1....0..2....0..2....2..1....1..1....2..1....1..2....2..0
..2..0....1..2....1..1....1..2....2..2....1..0....0..2....1..2....1..1....1..1
..1..0....0..1....2..2....1..0....2..2....2..2....0..1....1..0....2..0....2..2
..2..0....0..2....0..0....2..2....2..2....2..2....1..1....2..1....0..0....0..0
..2..1....1..1....0..1....0..1....2..2....0..1....2..0....0..2....1..2....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 14 2013
STATUS
approved