OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3).
Conjectures from Colin Barker, Oct 19 2018: (Start)
G.f.: 8*x*(44 - 237*x + 256*x^2) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).
a(n) = 4*(42 + 21*2^n + 4^n).
(End)
EXAMPLE
Some solutions for n=4:
..3..1..3..3....1..3..1..3....3..3..1..3....2..2..2..2....2..3..0..2
..1..3..1..1....1..3..1..3....3..3..1..3....0..0..0..0....2..3..0..2
..1..3..1..1....1..3..1..3....1..1..3..1....1..1..1..1....2..3..0..2
..3..1..3..3....1..3..1..3....1..1..3..1....1..1..1..1....2..3..0..2
..3..1..3..3....3..1..3..1....3..3..1..3....1..1..1..1....2..3..0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2014
STATUS
approved