OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) + 6*a(n-2) - a(n-3) - 2*a(n-4).
Empirical g.f.: x^2*(3 + 2*x) / ((1 + x)*(1 - 5*x - x^2 + 2*x^3)). - Colin Barker, Feb 06 2019
EXAMPLE
Some solutions for n=4:
..0..1. .0..2. .0..1. .0..2. .0..2. .0..2. .0..1. .0..2. .0..2. .0..2
..2..2. .1..1. .1..2. .1..2. .1..0. .1..1. .0..2. .1..0. .1..1. .1..0
..1..0. .1..0. .1..0. .0..0. .0..1. .2..1. .0..1. .1..2. .2..1. .0..2
..0..2. .2..1. .1..2. .2..1. .0..2. .0..0. .0..0. .0..1. .0..2. .1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 05 2016
STATUS
approved