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 A213984 #7 Jul 22 2025 23:05:32 %S A213984 2,24,1003,120133,35799856,24651985100 %N A213984 Number of n X n 0..2 matrices whose square is also a 0..2 matrix. %C A213984 Column 2 of A213990 %e A213984 Some solutions for n=3 %e A213984 ..0..1..1....1..0..1....0..2..0....0..1..0....1..1..2....0..0..0....0..1..2 %e A213984 ..0..0..2....0..0..2....0..0..0....0..1..2....0..0..0....0..0..0....1..0..0 %e A213984 ..0..0..0....0..1..0....0..0..0....0..0..0....0..0..0....0..0..0....0..1..0 %K A213984 nonn %O A213984 1,1 %A A213984 _R. H. Hardin_ Jun 30 2012