OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) - 3*a(n-4) - 2*a(n-5) - a(n-6) for n>7.
Empirical g.f.: x^2*(1 + x)*(2 - 3*x - x^2 + x^4) / (1 - 3*x - x^2 + 3*x^4 + 2*x^5 + x^6). - Colin Barker, Feb 08 2019
EXAMPLE
Some solutions for n=4:
..0..1. .0..1. .0..1. .0..0. .0..1. .0..0. .0..1. .0..0. .0..0. .0..0
..0..1. .0..1. .0..1. .1..1. .0..1. .1..1. .0..1. .1..1. .1..0. .1..1
..0..1. .1..1. .1..0. .0..0. .0..0. .1..0. .0..1. .0..1. .1..0. .1..1
..0..0. .0..0. .1..0. .1..1. .1..1. .1..0. .0..1. .0..1. .1..1. .0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 13 2016
STATUS
approved