OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) - 2*a(n-2) + 9*a(n-3) - 4*a(n-4) + 9*a(n-5) - 9*a(n-6) for n>7.
Empirical g.f.: x*(48 + 3*x + 154*x^2 - 111*x^3 + 141*x^4 - 239*x^5 + 102*x^6) / (1 - 2*x + 2*x^2 - 9*x^3 + 4*x^4 - 9*x^5 + 9*x^6). - Colin Barker, Dec 28 2018
EXAMPLE
Some solutions for n=4:
..0..0..0....1..0..0....0..0..0....0..1..0....0..0..0....0..1..0....0..0..0
..1..0..0....0..0..1....1..0..0....0..1..0....0..0..0....0..1..0....0..0..1
..0..1..0....0..0..0....0..1..0....0..0..1....0..1..0....0..0..0....0..1..0
..0..0..0....0..1..0....1..0..0....0..0..0....0..0..1....1..0..0....0..1..0
..0..0..0....0..1..0....0..0..0....0..0..0....0..0..0....0..1..0....0..0..0
..0..1..0....1..0..0....0..1..0....0..1..0....0..0..0....0..1..0....0..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 20 2015
STATUS
approved