OFFSET
1,1
COMMENTS
Column 1 of A231419.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) - 11*a(n-3) + 4*a(n-4).
Empirical g.f.: x*(9 - 4*x - 15*x^2 + 6*x^3) / (1 - 6*x + 11*x^3 - 4*x^4). - Colin Barker, Feb 21 2018
EXAMPLE
Some solutions for n=5:
..0..1....0..0....0..1....0..1....0..0....0..1....0..1....0..1....0..1....0..1
..0..2....1..2....0..2....0..2....1..2....0..1....1..2....0..1....0..2....2..1
..0..1....1..2....0..1....0..1....0..1....1..2....0..2....1..0....2..1....2..0
..2..1....1..0....2..1....1..0....2..0....1..0....2..1....2..2....0..1....1..0
..2..0....1..2....0..2....2..0....1..2....2..2....2..0....0..1....1..2....1..0
..0..1....0..0....0..2....2..0....0..1....1..1....2..1....0..1....1..2....2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 08 2013
STATUS
approved