OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + 4*a(n-2) - 2*a(n-3) for n>4.
Empirical g.f.: 3*x*(9 - 9*x - 8*x^2 + 4*x^3) / (1 - 3*x - 4*x^2 + 2*x^3). - Colin Barker, Oct 06 2018
EXAMPLE
Some solutions for n=5:
..2..2..2..1..2....0..1..0..0..0....1..2..2..2..1....2..1..2..1..2
..2..2..2..2..2....0..1..0..0..0....1..2..1..2..2....2..1..2..1..0
..2..2..1..2..2....2..1..0..1..0....1..0..1..2..2....2..1..2..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 02 2013
STATUS
approved