OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) + 9*a(n-2) + 18*a(n-3).
Empirical g.f.: 6*x^2*(2 + x) / (1 - 6*x - 9*x^2 - 18*x^3). - Colin Barker, Sep 22 2018
EXAMPLE
Some solutions for n=3:
..0..1....0..2....0..0....0..2....0..2....0..1....0..2....0..0....0..1....0..2
..1..2....1..0....2..1....1..2....1..2....0..2....1..2....1..1....2..0....1..0
..1..1....0..2....1..0....1..0....0..2....2..1....2..0....0..2....2..2....2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 22 2013
STATUS
approved