OFFSET
1,2
COMMENTS
Column 2 of A221655.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) + a(n-3) for n>4.
Empirical g.f.: x*(1 - x)*(1 + x)^2 / (1 - 3*x - x^2 - x^3). - Colin Barker, Mar 14 2018
EXAMPLE
Some solutions for n=3:
..0..2....0..1....1..1....2..1....1..1....0..1....0..1....1..1....0..2....1..1
..2..1....2..1....1..1....0..0....0..2....2..2....1..2....1..2....2..0....0..1
..1..0....1..1....1..1....1..2....2..0....1..0....2..0....1..0....1..1....2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 21 2013
STATUS
approved