OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-1) - 8*a(n-2) - 30*a(n-3) - 24*a(n-4) - 8*a(n-5) - a(n-6).
Empirical g.f.: 2*x^2*(1 + x)*(1 + 5*x - 5*x^2 - 3*x^3) / (1 - 4*x - 4*x^2 - x^3)^2. - Colin Barker, Feb 15 2019
EXAMPLE
Some solutions for n=4:
..0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..0. .0..0. .0..1. .0..1
..1..0. .1..0. .0..2. .1..0. .1..2. .0..2. .1..2. .1..2. .0..2. .0..1
..1..2. .1..2. .1..2. .0..2. .2..0. .0..1. .0..2. .1..1. .1..2. .2..2
..0..2. .0..0. .1..2. .0..1. .2..0. .1..2. .0..0. .2..0. .2..1. .0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 15 2017
STATUS
approved