OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 3*a(n-2) + 9*a(n-3) - 4*a(n-4) - 12*a(n-5) - 4*a(n-6).
Empirical g.f.: x*(4 + 8*x + 5*x^2 - 16*x^3 - 16*x^4 - 4*x^5) / (1 - x - 3*x^2 - 9*x^3 + 4*x^4 + 12*x^5 + 4*x^6). - Colin Barker, Feb 23 2019
EXAMPLE
Some solutions for n=7:
..0..0. .0..1. .0..0. .0..0. .0..0. .0..0. .1..0. .1..0. .0..0. .1..0
..1..0. .0..0. .0..1. .1..0. .0..0. .0..0. .0..1. .0..0. .0..1. .1..0
..0..0. .1..0. .0..1. .0..0. .1..1. .0..1. .0..0. .0..1. .0..1. .0..0
..1..1. .1..0. .1..1. .0..0. .1..1. .0..0. .0..0. .0..0. .1..1. .0..0
..0..0. .0..0. .1..0. .0..0. .0..0. .0..1. .1..0. .0..0. .0..1. .0..0
..1..1. .1..1. .0..1. .1..1. .0..0. .0..0. .0..0. .0..0. .0..1. .0..1
..1..1. .1..1. .0..0. .0..0. .0..1. .1..0. .1..1. .1..1. .0..0. .0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 17 2017
STATUS
approved