OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-1) - 16*a(n-2) for n>4.
Conjectures from Colin Barker, Sep 17 2018: (Start)
G.f.: x*(1 - 2*x + 10*x^2 + 8*x^3) / (1 - 4*x)^2.
a(n) = 2^(2*n-5) * (10*n-9) for n>2.
(End)
EXAMPLE
Some solutions for n=4:
..0..1....0..0....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..0
..2..0....1..2....2..0....2..2....2..3....2..0....2..0....2..3....2..1....1..2
..0..2....3..1....1..2....3..0....0..2....2..3....0..3....1..2....0..3....3..0
..3..0....2..3....2..0....2..3....2..0....1..2....2..0....1..0....2..0....1..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 24 2013
STATUS
approved