OFFSET
1,1
COMMENTS
Column 1 of A251428.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) +2*a(n-2) -4*a(n-3).
Conjectures from Colin Barker, Mar 20 2018: (Start)
G.f.: 2*x*(1 + 4*x - 8*x^2) / ((1 - 2*x)*(1 - 2*x^2)).
a(n) = 2*(2^(n/2) + 2^n) for n even.
a(n) = 2*(2^n - 2^((n-3)/2+1)) for n odd.
(End)
EXAMPLE
Some solutions for n=10:
..1....0....1....1....0....0....0....1....1....0....1....1....1....0....1....0
..0....1....1....0....1....1....1....0....0....1....0....1....1....1....0....0
..0....1....1....0....1....0....0....0....1....0....0....1....1....0....0....1
..0....1....0....0....1....0....0....1....0....1....1....1....1....0....1....1
..1....1....1....1....1....0....1....0....0....0....0....0....0....1....0....0
..1....1....0....1....1....0....1....0....1....0....1....1....0....0....0....1
..0....1....0....0....0....0....0....1....0....1....0....0....1....0....0....0
..1....1....0....0....0....1....0....1....0....0....1....0....1....1....0....1
..1....1....0....1....0....0....0....0....1....1....0....0....0....1....0....1
..1....1....0....0....0....0....0....0....0....0....0....0....1....0....0....0
..0....1....1....0....0....0....1....1....1....1....1....0....1....1....1....1
..0....0....1....0....1....1....0....0....1....1....0....0....0....1....0....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 02 2014
STATUS
approved