OFFSET
1,4
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) - 3*a(n-2) - 12*a(n-3) - 27*a(n-4) - 18*a(n-5) - 9*a(n-6).
Empirical g.f.: x^3 / (1 - 3*x - 3*x^2 - 3*x^3)^2. - Colin Barker, Feb 20 2019
EXAMPLE
All solutions for n=4:
..1..1. .0..1. .1..1. .1..0. .0..0. .1..1
..1..1. .1..1. .1..1. .1..1. .1..1. .1..1
..1..1. .1..1. .1..1. .1..1. .1..1. .1..1
..1..0. .1..1. .0..0. .1..1. .1..1. .0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 13 2017
STATUS
approved