OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) + 9*a(n-2) - 54*a(n-3).
Conjectures from Colin Barker, Dec 31 2018: (Start)
G.f.: 3*x*(2 - 7*x - 18*x^2) / ((1 - 3*x)*(1 + 3*x)*(1 - 6*x)).
a(n) = 3^(n-2)*(14 + 2^(2+n)) / 2 for n even.
a(n) = 3^(n-2)*(28 + 2^(2+n)) / 2 for n odd.
(End)
EXAMPLE
Some solutions for n=4:
..0..0..0..0....0..1..1..0....1..0..0..1....0..0..1..1....1..1..1..1
..0..0..0..0....0..1..1..0....1..1..1..1....0..0..1..1....0..0..0..0
..0..0..0..0....0..0..0..0....0..1..1..0....1..0..0..1....1..1..0..0
..1..0..0..1....1..0..0..1....1..0..0..1....1..1..1..1....0..0..1..1
..1..0..0..1....1..0..0..1....1..0..0..1....0..1..1..0....1..1..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 18 2015
STATUS
approved