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 A222823 #5 Jul 23 2025 03:06:11 %S A222823 452,2052,5584,12476,23568,41668,67136,104112,153604,219728,303468, %T A222823 412720,545012,709272,907828,1146704,1426212,1759348,2142176,2590236, %U A222823 3101848,3686444,4346808,5102188,5942936 %N A222823 Number of idempotent 4X4 0..n matrices. %C A222823 Row 4 of A222821 %e A222823 Some solutions for n=3 %e A222823 ..0..0..0..2....1..1..2..0....0..0..0..0....0..3..3..2....0..1..2..1 %e A222823 ..0..0..3..0....0..0..0..0....2..1..3..0....0..0..0..0....0..1..1..0 %e A222823 ..0..0..1..0....0..0..0..0....0..0..0..0....0..1..1..0....0..0..0..0 %e A222823 ..0..0..0..1....0..0..3..1....2..0..2..1....0..0..0..1....0..0..1..1 %K A222823 nonn %O A222823 1,1 %A A222823 _R. H. Hardin_ Apr 09 2013