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 20 2018: (Start)
G.f.: 8*x*(560 - 3261*x + 4096*x^2) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).
a(n) = 4*(930 + 93*2^n + 4^n).
(End)
EXAMPLE
Some solutions for n=4:
..3..2..0..1..3..0....1..0..3..3..1..2....2..2..2..1..1..1....3..0..3..0..0..3
..3..2..0..1..3..0....1..0..3..3..1..2....2..2..2..1..1..1....3..0..3..0..0..3
..3..2..0..1..3..0....1..0..3..3..1..2....2..2..2..1..1..1....0..3..0..3..3..0
..3..2..0..1..3..0....1..0..3..3..1..2....1..1..1..2..2..2....3..0..3..0..0..3
..3..2..0..1..3..0....1..0..3..3..1..2....2..2..2..1..1..1....3..0..3..0..0..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 16 2014
STATUS
approved