OFFSET
1,1
COMMENTS
Column 2 of A218765.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-2) + 3*a(n-3) + 2*a(n-5) + 2*a(n-6) - 2*a(n-7).
Empirical g.f.: x*(2 + 2*x + 4*x^2 - x^3 + 4*x^4 - 2*x^6) / (1 - 2*x - x^2 - 3*x^3 - 2*x^5 - 2*x^6 + 2*x^7). - Colin Barker, Mar 10 2018
EXAMPLE
Some solutions for n=3:
..1..1....0..0....0..1....0..0....1..0....0..0....0..0....0..1....0..0....0..0
..0..0....0..0....0..0....0..1....0..0....0..0....1..0....0..0....1..0....0..0
..0..0....1..1....1..0....1..1....0..0....1..0....0..0....0..0....1..1....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 05 2012
STATUS
approved