OFFSET
1,1
COMMENTS
Column 3 of A220935.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) + 6*a(n-2).
Conjectures from Colin Barker, Mar 13 2018: (Start)
G.f.: 2*x*(1 + 3*x) / ((1 + x)*(1 - 6*x)).
a(n) = (2^n*3^(n+1) + 4) / 7 for n even.
a(n) = (2^n*3^(n+1) - 4) / 7 for n odd
(End)
EXAMPLE
Some solutions for n=3:
..0..1..0....0..1..1....0..1..0....0..0..0....0..0..0....0..1..0....0..0..0
..0..0..1....1..0..1....0..1..0....1..0..1....0..0..1....0..0..0....0..1..0
..1..1..0....1..0..0....0..1..0....1..0..0....0..1..0....1..1..0....1..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 25 2012
STATUS
approved