OFFSET
1,1
COMMENTS
Also 0..2 arrays with no 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 25*a(n-1) -45*a(n-2) -963*a(n-3) +2025*a(n-4) +3645*a(n-5) -6561*a(n-6).
Empirical g.f.: 576*x*(16 - 76*x - 819*x^2 + 2124*x^3 + 3321*x^4 - 6561*x^5) / ((1 - 25*x + 90*x^2 - 81*x^3)*(1 - 45*x^2 - 81*x^3)). - Colin Barker, Jun 06 2018
EXAMPLE
Some solutions for n=5:
..2..1..1..1..0..1....0..0..2..1..0..2....2..2..1..2..2..1....1..1..2..2..2..1
..0..0..2..2..2..1....1..1..2..1..0..1....0..0..1..0..0..0....2..0..0..1..0..0
..2..1..1..0..0..0....0..0..2..1..0..2....1..2..2..2..1..2....1..1..2..1..2..2
..2..0..2..2..1..1....1..1..2..1..0..2....1..0..1..0..0..2....2..0..2..0..0..0
..1..1..1..0..0..0....2..0..2..1..0..2....2..2..1..2..1..2....1..0..2..1..2..1
..2..2..2..2..1..1....1..0..2..1..0..1....0..0..0..0..0..2....1..0..2..1..2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 10 2012
STATUS
approved