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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

%I #10 Apr 07 2020 15:25:55

%S 1,1,6,69,1620,62781,3710272,313568636,36218801244,5518184697792,

%T 1078258692423672,264082675302603684,79537577428138854144,

%U 28988656113108616134732,12610397520409429024276176,6469939930732195901177163384,3874562148530193751600746715440,2683567291732998871830525552934800

%N 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.

%C Number of n X n symmetric matrices with nonnegative integer entries and all row and column sums 5. - _Andrew Howroyd_, Apr 07 2020

%e All solutions for 10X2

%e ..1..1....1..1....1..1....1..1....1..0....1..1

%e ..1..1....1..0....1..1....1..1....1..0....1..1

%e ..1..1....1..0....1..1....1..0....1..0....1..1

%e ..1..1....1..0....1..1....1..0....1..0....1..0

%e ..1..0....1..0....1..1....1..0....1..0....1..0

%e ..0..1....0..1....0..0....0..1....0..1....0..1

%e ..0..0....0..1....0..0....0..1....0..1....0..1

%e ..0..0....0..1....0..0....0..1....0..1....0..0

%e ..0..0....0..1....0..0....0..0....0..1....0..0

%e ..0..0....0..0....0..0....0..0....0..1....0..0

%Y Row 5 of A188403.

%K nonn

%O 0,3

%A _R. H. Hardin_, Mar 30 2011

%E a(0)=1 prepended and terms a(10) and beyond from _Andrew Howroyd_, Apr 07 2020