A067210 Number of n X n 0..2 matrices with all row and column sums equal.

1, 3, 9, 87, 5673, 2577513, 8459809773, 207495141083975, 39125696231091082665, 57899300601363050181107733, 683382115404724657577266518831159, 65156055488094891194179319045960728827635, 50704966066306827486637758645370695372532720829085

Offset: 0

Author

R. H. Hardin, Feb 20 2002

Keywords

• nonn

Examples

			Some solutions for n=4
..1..1..0..1....0..0..2..1....2..0..1..1....2..0..2..2....2..1..1..0
..0..2..1..0....1..1..1..0....0..1..2..1....1..2..1..2....0..2..0..2
..2..0..0..1....2..0..0..1....2..1..0..1....1..2..2..1....1..0..2..1
..0..0..2..1....0..2..0..1....0..2..1..1....2..2..1..1....1..1..1..1
		

Crossrefs

Column k=2 of A202784.

Extensions

a(7) and example from R. H. Hardin, Jan 05 2012

a(8)-a(12) from Andrew Howroyd, Jun 01 2017

a(0)=1 prepended by Andrew Howroyd, Oct 14 2024