OFFSET
1,1
COMMENTS
Column 2 of A280859.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) + 8*a(n-3) - 8*a(n-4) for n>5.
Empirical g.f.: x*(1 - x)*(2 + 3*x - 4*x^3) / (1 - 4*x + 2*x^2 - 8*x^3 + 8*x^4). - Colin Barker, Mar 22 2018
EXAMPLE
Some solutions for n=4:
..0..0. .0..1. .0..1. .0..1. .0..1. .0..1. .0..0. .0..1. .0..0. .0..0
..1..2. .2..1. .2..2. .0..2. .0..2. .2..2. .1..2. .1..2. .1..1. .1..2
..1..0. .2..0. .1..0. .1..1. .1..1. .1..1. .0..0. .0..0. .0..2. .0..2
..0..2. .1..1. .0..2. .0..2. .2..2. .0..0. .1..1. .1..1. .1..0. .0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 09 2017
STATUS
approved