OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 9*a(n-3) + 12*a(n-4) - 2*a(n-5) - 3*a(n-6) + a(n-7) for n>8.
Empirical g.f.: x*(33 - 47*x - 66*x^2 + 131*x^3 - 41*x^4 - 23*x^5 + 14*x^6 - 2*x^7) / ((1 - x)^2*(1 - 2*x - 3*x^2 + 5*x^3 + x^4 - x^5)). - Colin Barker, Nov 16 2018
EXAMPLE
Some solutions for n=4:
..0..0..0..0..0....0..0..0..0..1....0..1..0..0..1....0..0..0..0..1
..0..0..0..0..1....0..0..0..1..1....1..0..1..1..1....0..0..1..1..1
..1..0..0..0..1....0..0..0..1..1....0..1..1..1..1....0..1..1..1..1
..0..1..0..1..1....1..1..0..1..1....1..1..1..1..1....1..1..1..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 27 2014
STATUS
approved