OFFSET
1,1
COMMENTS
Column 1 of A204616.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) - 2*a(n-3) for n>6.
Conjectures from Colin Barker, Feb 20 2018: (Start)
G.f.: (16 - x - 16*x^2 - 8*x^3 - 4*x^4 - x^5) / ((1 - x)*(1 - 2*x - 2*x^2)).
a(n) = (112 + (193-113*sqrt(3))*(1-sqrt(3))^n + (1+sqrt(3))^n*(193+113*sqrt(3))) / 24 for n>2.
(End)
EXAMPLE
Some solutions for n=4:
..1..1....1..0....0..0....0..0....1..1....1..1....1..0....1..0....0..0....1..1
..1..1....0..0....1..0....0..1....0..0....0..0....0..0....0..0....0..1....1..1
..1..1....0..1....0..0....0..0....0..0....0..0....1..0....0..1....0..1....1..1
..0..0....0..1....0..1....1..0....0..1....1..1....1..1....0..1....0..1....1..1
..1..1....0..0....0..1....1..0....0..1....1..1....0..1....0..1....0..1....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 17 2012
STATUS
approved