cp's OEIS Frontend

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.

%I A188400 #10 Apr 07 2020 14:55:38
%S A188400 1,76,2578,44288,478711,3710272,22393101,111200600,472211360,
%T A188400 1763603560,5916521021,18121655192,51328536740,135834620472,
%U A188400 338676787932,801091475448,1808025242415,3912600581712,8152010122276,16411466716600,32022153082291,60720959942432,112158519503545
%N 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.
%C A188400 Number of 6 X 6 symmetric matrices with nonnegative integer entries and all row and column sums n. - _Andrew Howroyd_, Apr 07 2020
%H A188400 Andrew Howroyd, <a href="/A188400/b188400.txt">Table of n, a(n) for n = 0..50</a>
%e A188400 Some solutions for 12X6
%e A188400 ..1..0..0..1..0..0....1..0..0..0..1..0....1..0..0..1..0..0....1..1..0..0..0..0
%e A188400 ..1..0..0..0..0..0....1..0..0..0..0..0....1..0..0..0..0..0....1..0..1..0..0..0
%e A188400 ..0..1..0..0..0..0....0..1..1..0..0..0....0..1..1..0..0..0....0..1..1..0..0..0
%e A188400 ..0..1..0..0..0..0....0..1..0..0..0..0....0..1..1..0..0..0....0..0..0..1..0..1
%e A188400 ..0..0..1..1..0..0....0..0..1..1..0..0....0..0..0..1..0..0....0..0..0..1..0..1
%e A188400 ..0..0..1..0..0..0....0..0..0..1..0..0....0..0..0..0..1..1....0..0..0..0..1..0
%e A188400 ..0..0..0..0..1..1....0..0..0..0..1..0....0..0..0..0..1..0....0..0..0..0..1..0
%e A188400 ..0..0..0..0..1..1....0..0..0..0..0..1....0..0..0..0..0..1....0..0..0..0..0..0
%e A188400 ..0..0..0..0..0..0....0..0..0..0..0..1....0..0..0..0..0..0....0..0..0..0..0..0
%e A188400 ..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0
%e A188400 ..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0
%e A188400 ..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0
%Y A188400 Column 6 of A188403.
%K A188400 nonn
%O A188400 0,2
%A A188400 _R. H. Hardin_, Mar 30 2011
%E A188400 a(0)=1 prepended and terms a(17) and beyond from _Andrew Howroyd_, Apr 07 2020