OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) + 4*a(n-3) + a(n-4) for n>5.
Empirical g.f.: 3*x*(1 + 4*x - 2*x^2 + 4*x^3 + x^4) / ((1 + x^2)*(1 - 4*x - x^2)). - Colin Barker, Jan 31 2019
EXAMPLE
Some solutions for n=4:
..0..1..1. .0..1..2. .0..1..1. .0..0..1. .0..1..2. .0..1..1. .0..1..2
..0..2..2. .1..1..2. .0..1..2. .0..1..1. .2..1..0. .1..2..2. .1..1..2
..2..2..0. .1..2..0. .1..2..0. .1..2..0. .1..0..0. .2..2..0. .1..2..0
..2..0..0. .2..2..0. .1..0..0. .1..0..0. .0..2..2. .2..1..0. .2..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 12 2016
STATUS
approved