OFFSET
1,2
COMMENTS
Column 3 of A221483.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..66
FORMULA
Empirical: a(n) = 8*a(n-1) - 7*a(n-2) - 24*a(n-3) + 6*a(n-4) for n>6.
Empirical g.f.: x^2*(8 - 14*x - 31*x^2 + 18*x^3 - 3*x^4) / (1 - 8*x + 7*x^2 + 24*x^3 - 6*x^4). - Colin Barker, Aug 05 2018
EXAMPLE
Some solutions for n=3:
..1..2..0....1..2..0....0..3..0....0..2..0....1..2..0....0..1..1....0..3..0
..0..2..1....1..2..1....2..0..1....1..3..1....0..2..2....1..3..1....1..1..0
..0..2..1....0..2..0....0..3..0....0..1..1....0..2..0....0..2..0....1..2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 17 2013
STATUS
approved