OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-3).
Empirical g.f.: 2*x*(1 + x + x^2) / (1 - 2*x - x^3). - Colin Barker, Oct 03 2018
EXAMPLE
Some solutions for n=7:
..0..1....2..1....2..1....2..1....1..2....0..1....1..2....2..1....0..1....0..1
..1..2....1..0....1..0....1..0....0..1....1..2....0..1....1..0....1..2....1..2
..0..1....0..1....2..1....2..1....1..0....0..1....1..2....0..1....0..1....0..1
..2..0....1..2....1..2....1..0....2..1....2..0....0..1....1..2....2..0....1..2
..0..1....2..0....2..1....2..1....1..0....1..2....2..0....2..1....1..2....2..1
..1..2....0..1....1..2....1..2....2..1....2..1....1..2....1..2....0..1....1..2
..0..1....1..2....0..1....2..1....1..2....1..0....2..1....2..1....1..2....2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 17 2013
STATUS
approved