OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) - 14*a(n-2) + 21*a(n-4) - 7*a(n-5) - 6*a(n-6).
Empirical g.f.: x*(2 - 10*x + 10*x^2 + 11*x^3 - 11*x^4 - 5*x^5) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - 3*x)*(1 - 2*x - x^2)). - Colin Barker, Jan 13 2019
EXAMPLE
Some solutions for n=10:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....1....0....0....1....0....1....0....0....0....0....0....1....1....1
..1....0....0....1....0....0....1....2....1....1....1....1....1....0....0....2
..2....0....2....1....1....2....1....0....2....1....1....0....2....2....1....1
..1....0....0....2....1....0....1....0....1....0....0....1....0....0....2....0
..2....1....0....1....1....1....1....0....1....2....1....1....2....0....0....1
..1....1....2....1....1....2....1....1....2....2....0....1....1....2....1....0
..1....0....0....0....1....0....0....2....0....0....0....2....2....1....2....0
..2....1....0....2....2....2....0....0....0....2....1....2....0....1....1....0
..1....2....2....1....0....0....2....1....1....0....2....1....0....2....2....2
..1....1....1....1....0....2....2....0....1....1....0....2....1....0....1....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 01 2016
STATUS
approved