A188400 Number of (6*n) X 6 binary arrays with rows in nonincreasing order, n ones in every column and no more than 2 ones in any row.

1, 76, 2578, 44288, 478711, 3710272, 22393101, 111200600, 472211360, 1763603560, 5916521021, 18121655192, 51328536740, 135834620472, 338676787932, 801091475448, 1808025242415, 3912600581712, 8152010122276, 16411466716600, 32022153082291, 60720959942432, 112158519503545

Offset: 0

Author

R. H. Hardin, Mar 30 2011

Keywords

• nonn

Comments

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

Examples

			Some solutions for 12X6
..1..0..0..1..0..0....1..0..0..0..1..0....1..0..0..1..0..0....1..1..0..0..0..0
..1..0..0..0..0..0....1..0..0..0..0..0....1..0..0..0..0..0....1..0..1..0..0..0
..0..1..0..0..0..0....0..1..1..0..0..0....0..1..1..0..0..0....0..1..1..0..0..0
..0..1..0..0..0..0....0..1..0..0..0..0....0..1..1..0..0..0....0..0..0..1..0..1
..0..0..1..1..0..0....0..0..1..1..0..0....0..0..0..1..0..0....0..0..0..1..0..1
..0..0..1..0..0..0....0..0..0..1..0..0....0..0..0..0..1..1....0..0..0..0..1..0
..0..0..0..0..1..1....0..0..0..0..1..0....0..0..0..0..1..0....0..0..0..0..1..0
..0..0..0..0..1..1....0..0..0..0..0..1....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..0..0..0..0....0..0..0..0..0..0
..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0
..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0
..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..50

Crossrefs

Column 6 of A188403.

Extensions

a(0)=1 prepended and terms a(17) and beyond from Andrew Howroyd, Apr 07 2020