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 A224114 #11 Feb 06 2023 12:47:59 %S A224114 0,0,1,0,1,21,0,1,51,282,0,1,93,1434,3070,0,1,147,4182,30410,29505,0, %T A224114 1,213,9762,136990,546465,260967,0,1,291,19110,467290,3784335,8815317, %U A224114 2175236,0,1,381,34602,1240310,18925485,94529631 %N A224114 T(n,k) = Number of idempotent n X n 0..k matrices of rank 2. %C A224114 Table starts: %C A224114 .......0.......0........0........0.......0.....0...0.0.0 %C A224114 .......1.......1........1........1.......1.....1...1.1 %C A224114 ......21......51.......93......147.....213...291.381 %C A224114 .....282....1434.....4182.....9762...19110.34602 %C A224114 ....3070...30410...136990...467290.1240310 %C A224114 ...29505..546465..3784335.18925485 %C A224114 ..260967.8815317.94529631 %C A224114 .2175236 %e A224114 Some solutions for n=3, k=4: %e A224114 ..1..0..2....0..1..3....0..0..1....0..0..0....0..0..0....1..0..0....1..3..0 %e A224114 ..0..1..3....0..1..0....0..1..0....3..1..0....0..1..0....0..1..1....0..0..0 %e A224114 ..0..0..0....0..0..1....0..0..1....3..0..1....4..0..1....0..0..0....0..3..1 %Y A224114 Row 3 is A224334. %K A224114 nonn,tabl,more %O A224114 1,6 %A A224114 _R. H. Hardin_, Apr 09 2013