OFFSET
1,1
COMMENTS
Column 1 of A238775.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-2) + 2*a(n-3).
Empirical g.f.: x*(3 + 3*x + 2*x^2) / (1 - x - 2*x^2 - 2*x^3). - Colin Barker, Feb 24 2018
EXAMPLE
Some solutions for n=5:
..3....3....2....1....1....2....1....3....2....1....3....3....1....1....2....1
..1....1....3....2....2....3....3....2....3....3....1....2....2....2....1....3
..2....2....3....1....2....3....1....2....2....3....2....3....2....2....2....2
..1....3....1....3....3....3....2....2....2....2....1....1....3....2....2....1
..1....3....3....2....1....1....2....2....2....2....2....2....3....1....2....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 05 2014
STATUS
approved