OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3) - a(n-4).
Empirical g.f.: x*(4 - 11*x + 7*x^2 - x^3) / (1 - 3*x + x^2)^2. - Colin Barker, Jan 17 2019
EXAMPLE
Some solutions for n=4:
..1..0. .1..1. .1..0. .0..0. .1..0. .1..1. .0..0. .1..0. .0..0. .1..1
..0..1. .0..0. .0..1. .1..0. .1..0. .0..0. .0..0. .0..0. .1..0. .0..1
..0..1. .1..0. .0..0. .1..0. .0..0. .1..0. .0..1. .1..0. .0..0. .0..0
..1..0. .1..0. .1..0. .0..1. .0..1. .0..0. .1..0. .0..1. .1..1. .1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 17 2016
STATUS
approved