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 A222833 #7 Jul 23 2025 03:07:51 %S A222833 1,7,72,600,4032,24576,138240,743424,3833856,19267584,94371840, %T A222833 454557696 %N A222833 Number of n X n 0..3 arrays with no element equal to another at a city block distance of exactly two, and new values 0..3 introduced in row major order. %C A222833 Diagonal of A222838 %e A222833 Some solutions for n=4 %e A222833 ..0..1..1..2....0..1..1..0....0..1..2..2....0..1..2..0....0..1..2..3 %e A222833 ..3..2..0..0....0..2..3..3....2..3..3..0....0..3..3..0....3..1..2..3 %e A222833 ..1..2..3..1....1..2..0..1....2..0..1..1....2..2..1..1....2..0..0..1 %e A222833 ..0..0..3..1....1..3..0..1....1..0..2..2....3..0..0..2....2..3..3..2 %K A222833 nonn %O A222833 1,2 %A A222833 _R. H. Hardin_ Mar 06 2013