OFFSET
1,1
COMMENTS
Column 1 of A183508.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 3*a(n-1) + 3*a(n-3) - 9*a(n-4).
Empirical g.f.: 3*x*(1 + x)*(1 - 3*x^2) / ((1 - 3*x)*(1 - 3*x^3)). - Colin Barker, Mar 29 2018
EXAMPLE
Some solutions for 3 X 1:
..3....3....3....2....0....3....1....1....2....2....0....0....1....0....2....0
..0....1....1....0....2....2....0....3....1....0....3....3....2....1....3....3
..2....0....3....3....0....0....1....0....0....1....1....2....3....0....0....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 05 2011
STATUS
approved