OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) - a(n-3) - a(n-5) + a(n-6) - a(n-7).
Empirical g.f.: x*(39 - 6*x - 16*x^2 - 4*x^3 - 11*x^4 + 9*x^5 - 14*x^6) / ((1 - x)*(1 + x)*(1 - 3*x + x^2 - 2*x^3 + x^4 - x^5)). - Colin Barker, Nov 03 2018
EXAMPLE
Some solutions for n=6:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....1....1....1....0....1....1....0....1....0....0....1....0....1....1
..2....0....0....0....1....1....1....2....0....0....0....1....1....1....0....1
..0....2....0....2....0....1....0....2....1....2....1....1....1....1....0....2
..0....1....2....0....1....0....0....2....0....1....0....2....2....1....2....0
..2....2....2....0....2....1....1....0....2....1....0....1....1....2....1....2
..2....2....0....0....1....2....2....0....1....0....1....0....1....2....0....1
..1....2....2....1....2....2....0....0....1....0....2....2....0....1....2....1
..0....0....2....1....2....1....0....0....1....2....2....0....2....1....2....0
..1....1....2....2....1....1....2....2....0....0....0....1....0....2....1....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 04 2014
STATUS
approved