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 A213988 #6 Jul 22 2025 23:06:00 %S A213988 3,126,28328,29365738,124477495732 %N A213988 Number of n X n 0..6 matrices whose square is also a 0..6 matrix. %C A213988 Column 6 of A213990 %e A213988 Some.solutions.for.n=3 %e A213988 ..2..0..1....0..1..0....0..6..4....0..3..6....0..4..0....0..5..0....0..0..4 %e A213988 ..0..1..6....0..0..1....0..1..0....0..1..0....0..0..0....0..1..0....0..1..3 %e A213988 ..0..0..0....3..3..0....0..0..0....0..0..0....1..5..0....0..3..0....0..1..1 %K A213988 nonn %O A213988 1,1 %A A213988 _R. H. Hardin_ Jun 30 2012