OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) - 8*a(n-2).
Conjectures from Colin Barker, Oct 19 2018: (Start)
G.f.: 8*x*(5 - 16*x) / ((1 - 2*x)*(1 - 4*x)).
a(n) = 2^(2+n) * (3+2^n).
(End)
EXAMPLE
Some solutions for n=4:
..0..0....1..1....1..1....3..3....3..3....0..2....3..3....3..3....0..0....2..1
..3..3....2..2....3..3....2..2....2..2....0..2....3..3....2..2....1..1....2..1
..2..2....2..2....3..3....0..0....3..3....0..2....3..3....2..2....0..0....1..2
..3..3....1..1....2..2....0..0....3..3....0..2....2..2....1..1....2..2....1..2
..1..1....3..3....2..2....0..0....1..1....2..0....2..2....3..3....2..2....1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2014
STATUS
approved