This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A188450 #6 Jul 22 2025 11:13:05 %S A188450 0,1,8,66,722,9955,165252,3221806,72445292,1851203574,53113148720, %T A188450 1694163830194,59579694687012 %N A188450 Number of (2*n)Xn binary arrays with nonzero rows in decreasing order, no more than 3 ones in any row and exactly 2 ones in every column. %C A188450 Row 2 of A188449 %e A188450 Some solutions for 6X3 %e A188450 ..1..1..1....1..1..0....1..1..1....1..0..1....1..1..0....1..1..1....1..1..1 %e A188450 ..1..0..1....1..0..1....1..0..0....1..0..0....1..0..1....1..0..0....1..1..0 %e A188450 ..0..1..0....0..1..0....0..1..1....0..1..1....0..1..1....0..1..0....0..0..1 %e A188450 ..0..0..0....0..0..1....0..0..0....0..1..0....0..0..0....0..0..1....0..0..0 %e A188450 ..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0 %e A188450 ..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0 %K A188450 nonn %O A188450 1,3 %A A188450 _R. H. Hardin_ Mar 31 2011