OFFSET
1,2
COMMENTS
Column 3 of A229685.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 18*a(n-1) -108*a(n-2) +216*a(n-3) for n>4.
Empirical: G.f. 12*x^2*(10*x+1)*(10*x-3) / (6*x-1)^3. - R. J. Mathar, Sep 29 2013
Empirical a(n) = 2^n*3^(n-3)*(-45 + 4*n + 16*n^2) for n>1. - Colin Barker, Jun 16 2017
EXAMPLE
Some solutions for n=3
..0..0..0....0..0..0....0..0..1....0..0..1....0..0..0....0..1..2....0..1..1
..1..2..2....1..1..2....0..1..2....2..2..0....0..1..1....2..2..0....2..2..2
..0..2..2....1..1..2....0..1..0....2..1..0....0..2..1....1..2..0....1..2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 27 2013
STATUS
approved