Some solutions for n=4 with a(1,1)=0
..0..0..0..0....0..1..0..0....0..1..0..0....0..0..1..0....0..1..0..1
..0..1..1..1....1..1..0..1....1..1..1..1....0..1..1..0....1..1..0..1
..0..1..1..0....0..0..1..0....0..1..0..0....1..1..1..0....0..0..0..0
..0..1..0..0....0..1..0..1....0..1..0..1....0..0..0..0....1..1..0..1
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