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 A230749 #6 Jul 23 2025 05:59:35 %S A230749 12,5544,13305708,116879941620,5769362600920812, %T A230749 1504181314566629793432,2135728868490621147879828300, %U A230749 16459977111484024315408273362622152,689468967599129606177339374031370776847408 %N A230749 Number of (n+3)X(n+3) 0..2 arrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 3, and upper left element zero. %C A230749 Diagonal of A230757 %e A230749 Some solutions for n=1 %e A230749 ..0..0..0..0....0..2..2..0....0..2..2..2....0..2..0..0....0..0..2..0 %e A230749 ..2..1..1..2....0..1..1..0....1..1..0..0....0..1..1..2....2..1..1..0 %e A230749 ..2..1..1..2....0..1..1..0....0..0..1..1....2..1..1..0....0..1..1..2 %e A230749 ..0..0..0..0....0..2..2..0....2..2..2..0....0..0..2..0....0..2..0..0 %K A230749 nonn %O A230749 1,1 %A A230749 _R. H. Hardin_, Oct 29 2013