OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 4*a(n-2) + 2*a(n-3) for n>4.
Empirical g.f.: x*(1 - x^2 + x^3) / (1 - 4*x + 4*x^2 - 2*x^3). - Colin Barker, Feb 05 2019
EXAMPLE
Some solutions for n=4:
..0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1
..0..2. .2..1. .0..1. .0..2. .2..0. .0..2. .0..1. .0..1. .0..1. .2..1
..0..1. .2..1. .0..2. .0..1. .1..2. .0..2. .2..1. .0..2. .0..1. .2..1
..0..2. .0..1. .0..1. .0..1. .0..1. .0..2. .2..1. .1..2. .0..2. .2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 28 2016
STATUS
approved