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 A202649 #7 Jul 22 2025 16:45:25 %S A202649 3,52,8460,14394092,231197740500 %N A202649 Number of n X n 0..2 arrays with no row or column sum equal to the previous. %C A202649 Column 2 of A202651 %e A202649 Some solutions for n=3 %e A202649 ..0..2..1....0..2..1....2..2..1....1..0..0....0..2..0....0..0..1....0..0..0 %e A202649 ..1..2..1....2..1..1....0..2..0....2..2..2....2..2..0....2..2..0....1..2..1 %e A202649 ..1..2..0....1..1..0....1..1..2....1..0..1....0..1..0....2..1..0....2..0..0 %K A202649 nonn %O A202649 1,1 %A A202649 _R. H. Hardin_ Dec 22 2011