OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 4*a(n-2).
Conjectures from Colin Barker, Dec 25 2018: (Start)
G.f.: 2*x*(5 + 8*x) / (1 - x - 4*x^2).
a(n) = (2^(1-n)*((1-sqrt(17))^n*(-4+sqrt(17)) + (1+sqrt(17))^n*(4+sqrt(17)))) / sqrt(17).
(End)
EXAMPLE
Some solutions for n=4:
..1..0....1..0....1..0....1..0....1..1....1..0....1..0....0..0....0..1....1..1
..1..1....0..1....0..1....1..1....0..1....0..0....0..1....1..0....1..0....0..1
..0..1....1..1....1..0....1..0....0..0....1..0....1..1....0..0....1..1....1..1
..0..0....0..1....0..0....1..1....1..0....0..0....0..1....0..1....0..1....1..0
..1..0....1..1....0..1....1..0....0..0....1..0....0..0....1..0....1..1....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jun 23 2015
STATUS
approved