OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 7*a(n-2) + 2*a(n-3) - 2*a(n-4).
Empirical g.f.: x*(2 + 5*x + 2*x^2 - 2*x^3) / ((1 + x)*(1 - 3*x - 4*x^2 + 2*x^3)). - Colin Barker, Jan 30 2019
EXAMPLE
Some solutions for n=4:
..0..1..0..2. .0..1..2..0. .0..1..0..1. .0..1..0..1. .0..1..0..1
..2..0..1..0. .1..2..1..2. .1..2..1..0. .1..2..1..2. .2..0..1..2
..1..2..0..2. .2..0..2..1. .0..1..2..1. .0..1..2..0. .0..2..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 04 2016
STATUS
approved