OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) - 2*a(n-2) for n>5.
Empirical: a(n) = 9*2^(n-1) + 48 for n>3.
Empirical g.f.: x*(69 - 134*x + 4*x^2 + 11*x^3 + 2*x^4) / ((1 - x)*(1 - 2*x)). - Colin Barker, Dec 12 2018
EXAMPLE
Some solutions for n=4:
..1..0..0..1..1....1..0..1..0..0....0..0..0..0..0....1..1..0..1..0
..1..0..0..1..1....1..0..1..0..0....1..1..1..1..1....1..1..0..1..0
..1..0..0..1..1....1..0..1..0..0....0..0..0..0..0....1..1..0..1..0
..1..0..0..1..1....1..0..1..0..1....0..0..0..0..1....1..1..0..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 31 2014
STATUS
approved