A188407 Number of (6*n) X n binary arrays with rows in nonincreasing order, 6 ones in every column and no more than 2 ones in any row.

1, 1, 7, 106, 3616, 222190, 22393101, 3444274966, 767013376954, 237357745294502, 98772845166962126, 53805754052806007528, 37518059561068661124848, 32857132982034738756201764, 35557273023840891076852950650, 46882317669656858737974124606500, 74388988137861405036759725929161668

Offset: 0

Author

R. H. Hardin, Mar 30 2011

Keywords

• nonn

Comments

Number of n X n symmetric matrices with nonnegative integer entries and all row and column sums 6. - Andrew Howroyd, Apr 07 2020

Examples

			All solutions for 12X2
..1..0....1..1....1..1....1..1....1..1....1..1....1..1
..1..0....1..1....1..0....1..1....1..1....1..1....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..1....1..1....1..0
..1..0....1..0....1..0....1..0....1..1....1..1....1..0
..1..0....1..0....1..0....1..0....1..0....1..1....1..0
..0..1....0..1....0..1....0..1....0..1....0..0....0..1
..0..1....0..1....0..1....0..1....0..0....0..0....0..1
..0..1....0..0....0..1....0..1....0..0....0..0....0..1
..0..1....0..0....0..1....0..1....0..0....0..0....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..0....0..0....0..0
		

Crossrefs

Row 6 of A188403.

Extensions

a(0)=1 prepended and terms a(10) and beyond from Andrew Howroyd, Apr 06 2020