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 A230669 #7 Jun 02 2025 08:44:50 %S A230669 0,15,1173,730503,4022141121,169908632412447,55314799986833459367, %T A230669 140277459587738407279576815 %N A230669 Number of n X n 0..2 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value 2-x(i,j). %C A230669 Diagonal of A230675 %e A230669 Some solutions for n=3 %e A230669 ..2..2..0....1..1..1....1..2..0....0..1..0....1..1..0....1..1..2....2..0..1 %e A230669 ..0..0..0....0..2..2....0..1..0....1..2..1....2..2..0....1..0..0....1..1..1 %e A230669 ..2..2..2....2..0..2....0..2..0....0..1..1....0..0..0....0..2..0....2..0..2 %K A230669 nonn %O A230669 1,2 %A A230669 _R. H. Hardin_, Oct 27 2013