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

0,3

Links

Table of n, a(n) for n=0..15.

Example

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.

Sequence in context: A176315 A290758 A290769 * A239979 A336204 A261361

Adjacent sequences: A213791 A213792 A213793 * A213795 A213796 A213797

Keyword

nonn

Author

R. H. Hardin, Jun 20 2012

Extensions

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

Status

approved