OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-1) - 16*a(n-2).
Conjectures from Colin Barker, Jan 17 2019: (Start)
G.f.: 3*x*(3 - 4*x) / (1 - 4*x)^2.
a(n) = 4^(n-1) * (6*n+3).
(End)
EXAMPLE
Some solutions for n=4:
..0..0. .0..0. .0..1. .2..2. .1..2. .1..0. .2..2. .0..2. .2..1. .0..1
..0..2. .1..1. .0..0. .1..1. .2..0. .0..0. .2..1. .2..1. .0..2. .2..2
..2..2. .2..1. .2..2. .2..2. .0..1. .2..2. .2..1. .0..0. .1..2. .2..0
..1..0. .2..1. .2..2. .2..1. .2..1. .1..0. .2..2. .0..0. .2..2. .1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 16 2016
STATUS
approved