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A188406 Number of (5*n) X n binary arrays with rows in nonincreasing order, 5 ones in every column and no more than 2 ones in any row. 1
1, 1, 6, 69, 1620, 62781, 3710272, 313568636, 36218801244, 5518184697792, 1078258692423672, 264082675302603684, 79537577428138854144, 28988656113108616134732, 12610397520409429024276176, 6469939930732195901177163384, 3874562148530193751600746715440, 2683567291732998871830525552934800 (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 5. - Andrew Howroyd, Apr 07 2020

LINKS

Table of n, a(n) for n=0..17.

EXAMPLE

All solutions for 10X2

..1..1....1..1....1..1....1..1....1..0....1..1

..1..1....1..0....1..1....1..1....1..0....1..1

..1..1....1..0....1..1....1..0....1..0....1..1

..1..1....1..0....1..1....1..0....1..0....1..0

..1..0....1..0....1..1....1..0....1..0....1..0

..0..1....0..1....0..0....0..1....0..1....0..1

..0..0....0..1....0..0....0..1....0..1....0..1

..0..0....0..1....0..0....0..1....0..1....0..0

..0..0....0..1....0..0....0..0....0..1....0..0

..0..0....0..0....0..0....0..0....0..1....0..0

CROSSREFS

Row 5 of A188403.

Sequence in context: A235328 A296783 A218683 * A048708 A286527 A104900

Adjacent sequences:  A188403 A188404 A188405 * A188407 A188408 A188409

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 30 2011

EXTENSIONS

a(0)=1 prepended and terms a(10) and beyond from Andrew Howroyd, Apr 07 2020

STATUS

approved

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Last modified September 21 01:46 EDT 2021. Contains 347596 sequences. (Running on oeis4.)