OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + a(n-2) + 2*a(n-4) + a(n-6) for n>7.
Empirical g.f.: x*(36 + 5*x + 14*x^2 + 34*x^3 - 8*x^4 + 17*x^5 - 2*x^6) / (1 - x - x^2 - 2*x^4 - x^6). - Colin Barker, Dec 30 2018
EXAMPLE
Some solutions for n=4:
..1..0..0....0..1..0....0..1..0....1..0..1....0..1..0....1..0..0....1..0..0
..0..0..0....1..0..1....1..0..1....0..1..0....1..0..1....0..0..1....0..1..0
..1..0..1....0..0..0....0..1..0....0..1..0....0..0..0....1..0..0....1..0..1
..0..1..0....1..0..1....0..1..0....1..0..1....1..0..1....0..0..1....0..1..0
..1..0..1....0..1..0....1..0..1....0..1..0....0..1..0....1..0..0....0..0..1
..0..0..0....1..0..0....0..0..0....1..0..1....0..0..1....0..0..1....0..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 13 2015
STATUS
approved