OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) - 4*a(n-3).
Empirical g.f.: x*(8 + x - 6*x^2) / (1 - 7*x + 4*x^3). - Colin Barker, Feb 27 2019
EXAMPLE
Some solutions for n=5:
..1..1..1. .1..1..1. .0..0..1. .1..1..0. .1..0..0. .0..0..1. .1..1..0
..0..0..0. .0..1..1. .0..0..1. .1..1..0. .1..0..0. .0..0..0. .0..1..0
..1..1..1. .0..0..0. .1..1..0. .0..1..0. .0..0..0. .0..1..0. .0..0..0
..0..1..1. .1..1..0. .0..0..1. .1..1..1. .1..0..1. .0..1..1. .1..0..0
..0..0..1. .1..0..1. .0..0..0. .0..1..0. .0..0..1. .1..0..1. .1..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 29 2017
STATUS
approved