A188407 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

COMMENTS

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

LINKS

Table of n, a(n) for n=0..16.

EXAMPLE

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.

Sequence in context: A141362 A213863 A231899 * A075021 A138963 A141932

Adjacent sequences: A188404 A188405 A188406 * A188408 A188409 A188410

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 30 2011

EXTENSIONS

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

STATUS

approved