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 A231220 #6 Jul 23 2025 06:18:58 %S A231220 1,4,21,182,4298,117178,5930126,495739986 %N A231220 Number of (n+2)X(n+2) 0..2 arrays with no element unequal to a strict majority of its horizontal, vertical, diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order. %C A231220 Diagonal of A231227 %e A231220 Some solutions for n=4 %e A231220 ..0..0..0..0..0..0....0..0..0..1..1..1....0..0..0..0..1..1....0..0..0..1..1..1 %e A231220 ..0..0..1..1..0..0....0..0..0..1..1..1....0..0..0..0..1..1....0..0..0..1..1..1 %e A231220 ..1..1..1..1..1..1....1..1..1..0..0..0....0..0..0..0..1..1....0..0..1..1..1..1 %e A231220 ..1..1..1..1..1..1....1..1..1..0..0..0....0..0..0..0..1..1....1..1..1..1..1..1 %e A231220 ..2..2..2..2..2..2....0..0..0..1..1..1....0..0..0..0..1..1....1..1..1..1..1..1 %e A231220 ..2..2..2..2..2..2....0..0..0..1..1..1....0..0..0..0..1..1....1..1..1..1..1..1 %K A231220 nonn %O A231220 1,2 %A A231220 _R. H. Hardin_, Nov 05 2013