A188409 Number of (8*n) X n binary arrays with rows in nonincreasing order, 8 ones in every column and no more than 2 ones in any row.

1, 1, 9, 215, 13825, 1865715, 472211360, 205617134345, 144413237202513, 155491132440121969, 246331815235550280739, 555051611796729847585857, 1728979263188082473586904451, 7267279122553798970928760164349, 40366145202716102133415620482175732, 290962702320861139000003963988839815695

Offset

0,3

Comments

Number of n X n symmetric matrices with nonnegative integer entries and all row and column sums 8. - Andrew Howroyd, Apr 07 2020

Links

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

Example

All solutions for 16X2
..1..1....1..1....1..1....1..1....1..1....1..1....1..1....1..0....1..1
..1..1....1..1....1..1....1..0....1..1....1..1....1..1....1..0....1..1
..1..1....1..1....1..1....1..0....1..1....1..0....1..1....1..0....1..1
..1..1....1..1....1..1....1..0....1..1....1..0....1..1....1..0....1..0
..1..1....1..1....1..1....1..0....1..1....1..0....1..0....1..0....1..0
..1..0....1..1....1..1....1..0....1..1....1..0....1..0....1..0....1..0
..1..0....1..0....1..1....1..0....1..1....1..0....1..0....1..0....1..0
..1..0....1..0....1..0....1..0....1..1....1..0....1..0....1..0....1..0
..0..1....0..1....0..1....0..1....0..0....0..1....0..1....0..1....0..1
..0..1....0..1....0..0....0..1....0..0....0..1....0..1....0..1....0..1
..0..1....0..0....0..0....0..1....0..0....0..1....0..1....0..1....0..1
..0..0....0..0....0..0....0..1....0..0....0..1....0..1....0..1....0..1
..0..0....0..0....0..0....0..1....0..0....0..1....0..0....0..1....0..1
..0..0....0..0....0..0....0..1....0..0....0..1....0..0....0..1....0..0
..0..0....0..0....0..0....0..1....0..0....0..0....0..0....0..1....0..0
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..0

Crossrefs

Row 8 of A188403.

Sequence in context: A122399 A320096 A327198 * A109587 A067426 A250548

Adjacent sequences: A188406 A188407 A188408 * A188410 A188411 A188412

Keyword

nonn

Author

R. H. Hardin, Mar 30 2011

Extensions

a(0)=1 prepended and terms a(9) and beyond from Andrew Howroyd, Apr 06 2020

Status

approved