OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 16*a(n-2) - 7*a(n-3) - 18*a(n-4).
Empirical g.f.: 4*x*(1 + x)*(2 - 3*x) / (1 - 2*x - 16*x^2 + 7*x^3 + 18*x^4). - Colin Barker, Sep 12 2018
EXAMPLE
Some solutions for n=4:
..1..0..0..1....1..0..1..0....1..0..0..1....1..0..0..0....1..0..0..1
..0..0..0..0....0..0..0..0....1..0..0..1....0..0..1..0....0..0..0..0
..0..0..0..0....1..0..0..1....0..0..0..0....0..0..0..0....0..0..0..1
..0..1..0..0....1..0..0..0....0..0..0..0....1..0..0..1....1..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 29 2013
STATUS
approved