OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 3*a(n-2) - 3*a(n-3) for n>6.
Empirical g.f.: x*(28 + 5*x - 54*x^2 + 19*x^3 - 4*x^4 + 4*x^5) / ((1 - x)*(1 - 3*x^2)). - Colin Barker, Dec 30 2018
EXAMPLE
Some solutions for n=4:
..0..1..0....1..0..0....1..0..0....0..0..0....0..1..0....1..0..0....0..1..0
..0..0..1....0..0..0....0..1..0....1..0..1....0..1..0....0..1..0....1..0..1
..0..1..0....1..0..1....1..0..1....0..1..0....0..1..0....0..0..1....0..1..0
..1..0..1....0..0..0....0..0..0....1..0..1....0..1..0....0..1..0....1..0..0
..0..0..0....1..0..1....1..0..1....0..1..0....0..1..0....1..0..1....0..1..0
..1..0..0....0..1..0....0..0..0....0..0..1....0..1..0....0..1..0....0..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 08 2015
STATUS
approved