A213794 Number of n X n 0..2 symmetric arrays with every row summing to n.

1, 1, 3, 13, 169, 5673, 526443, 133721189, 95133854529, 190409704025737, 1081810465812816481, 17533275809917986947451, 814583187343481957681992873, 108889213625061640897043875544377, 42017261328544343771207789776696995237, 46930798910194830781686389018692804741926963

Offset: 0

Author

R. H. Hardin, Jun 20 2012

Keywords

• nonn

Examples

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

Crossrefs

Column 2 of A213800.

Extensions

a(0)=1 prepended and terms a(10) and beyond from Andrew Howroyd, Apr 07 2020