OFFSET
1,3
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-1) - 20*a(n-2) + 24*a(n-3) - 36*a(n-4) + 16*a(n-5) - 16*a(n-6).
Empirical g.f.: 2*x^3 / (1 - 4*x + 2*x^2 - 4*x^3)^2. - Colin Barker, Feb 20 2019
EXAMPLE
Some solutions for n=4:
..0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..1. .0..0
..1..0. .1..1. .0..0. .0..0. .1..0. .0..1. .0..1. .1..0. .0..0. .0..1
..0..0. .1..0. .0..1. .1..0. .0..0. .0..0. .0..0. .0..0. .0..1. .0..0
..0..0. .1..1. .0..0. .0..0. .1..1. .0..0. .1..0. .0..1. .0..0. .0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 04 2017
STATUS
approved