OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 4*a(n-2) - a(n-3) + 2*a(n-4).
Empirical g.f.: 2*x*(12 - 15*x - 3*x^2 + 8*x^3) / ((1 - x)*(1 - 2*x)*(1 - x - x^2)). - Colin Barker, Nov 20 2018
EXAMPLE
Some solutions for n=4:
..1..0..0..0..1....1..0..0..1..0....0..0..1..0..1....0..1..0..0..0
..1..0..0..0..1....1..0..0..1..1....0..0..0..1..0....0..1..0..0..0
..1..0..0..0..0....1..0..0..1..1....0..0..0..1..0....0..1..1..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 27 2014
STATUS
approved