OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) - 9*a(n-2) for n>4.
Conjectures from Colin Barker, Jan 17 2019: (Start)
G.f.: 3*x*(3 - x)*(1 + x - 4*x^2) / (1 - 3*x)^2.
a(n) = 16*3^(n-3) * (4*n+3) for n>2.
(End)
EXAMPLE
Some solutions for n=4:
..0..1..0..1. .2..2..1..2. .1..2..1..0. .2..1..0..0. .1..1..2..2
..0..0..0..2. .2..2..2..2. .2..2..1..0. .2..1..2..2. .2..2..2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 16 2016
STATUS
approved