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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.
2
1, 76, 2578, 44288, 478711, 3710272, 22393101, 111200600, 472211360, 1763603560, 5916521021, 18121655192, 51328536740, 135834620472, 338676787932, 801091475448, 1808025242415, 3912600581712, 8152010122276, 16411466716600, 32022153082291, 60720959942432, 112158519503545
OFFSET
0,2
COMMENTS
Number of 6 X 6 symmetric matrices with nonnegative integer entries and all row and column sums n. - Andrew Howroyd, Apr 07 2020
LINKS
EXAMPLE
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
CROSSREFS
Column 6 of A188403.
Sequence in context: A278092 A153177 A166191 * A205918 A261574 A017792
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 30 2011
EXTENSIONS
a(0)=1 prepended and terms a(17) and beyond from Andrew Howroyd, Apr 07 2020
STATUS
approved