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) - 4*a(n-3).
Conjectures from Colin Barker, Dec 09 2018: (Start)
G.f.: 4*x*(1 + x - 4*x^2) / ((1 - 2*x)*(1 - 2*x^2)).
a(n) = 2^(n/2+1) + 2^(n+1) for n even.
a(n) = 2^(n+1) for n odd.
(End)
EXAMPLE
Some solutions for n=10:
..1....1....0....0....0....0....0....1....0....1....0....0....0....1....1....0
..1....1....1....0....1....1....1....1....1....0....0....0....1....1....0....1
..0....0....1....0....1....0....1....0....1....0....0....0....1....1....0....1
..1....0....0....1....0....0....1....1....1....1....1....0....0....1....0....1
..0....0....0....0....0....0....1....1....0....0....0....0....0....1....0....0
..1....0....1....0....1....0....1....0....1....1....1....0....0....1....0....1
..0....1....1....1....0....0....0....0....0....0....1....0....0....0....0....1
..0....0....0....0....0....0....1....0....0....0....0....0....1....1....1....1
..1....0....0....1....0....1....1....0....1....1....1....0....0....1....0....1
..0....1....0....0....0....1....1....1....1....0....0....0....0....1....0....0
..1....0....0....1....1....0....0....1....0....1....1....1....0....1....0....0
..0....1....1....0....0....0....1....1....0....0....1....0....0....1....0....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 27 2014
STATUS
approved