OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4).
Empirical g.f.: 24*x^2*(1 - x)^2 / (1 - 2*x - 2*x^2)^2. - Colin Barker, Jan 18 2019
EXAMPLE
Some solutions for n=4:
..2..1..0..0. .2..2..2..1. .0..2..2..2. .2..2..1..2. .0..1..0..1
..2..1..2..1. .2..2..1..2. .2..1..2..1. .1..2..2..1. .2..0..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 18 2016
STATUS
approved