OFFSET
1,1
COMMENTS
Column 3 of A224409.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) + 2*a(n-3).
Empirical g.f.: x*(7 + 2*x^2) / (1 - 4*x + 2*x^2 - 2*x^3). - Colin Barker, Aug 30 2018
EXAMPLE
Some solutions for n=3:
..0..1..0....0..0..0....1..1..0....1..1..0....0..0..0....0..1..0....0..0..1
..1..1..0....0..0..0....1..1..1....1..0..0....0..1..0....1..0..0....1..1..0
..1..0..0....0..0..1....1..1..0....0..0..0....1..1..1....0..1..1....1..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 05 2013
STATUS
approved