OFFSET
1,2
COMMENTS
Column 3 of A231049.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) +19*a(n-2) +19*a(n-3) +12*a(n-4) -8*a(n-5) +8*a(n-6).
Empirical g.f.: 2*x^2*(1 - x)*(7 + 11*x + 8*x^2) / (1 - 3*x - 19*x^2 - 19*x^3 - 12*x^4 + 8*x^5 - 8*x^6). - Colin Barker, Feb 09 2018
EXAMPLE
Some solutions for n=4:
..0..3..0....0..1..0....0..1..0....0..1..2....0..1..2....0..1..2....0..1..2
..2..1..0....2..3..2....0..3..2....0..3..2....0..3..0....2..3..2....0..3..2
..2..1..2....2..1..0....2..3..0....2..3..0....0..3..0....1..0..1....0..3..2
..0..3..0....2..3..2....2..1..2....0..1..2....0..1..2....3..2..3....2..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 03 2013
STATUS
approved