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 A197402 #8 Jun 02 2025 04:53:50 %S A197402 1,9,60,3305,356211,93153650,77683473682,174585377113223 %N A197402 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 3,0,1,1,1 for x=0,1,2,3,4. %C A197402 Every 0 is next to 0 3's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 1's, every 4 is next to 4 1's %C A197402 Diagonal of A197409 %e A197402 Some solutions containing all values 0 to 4 for n=4 %e A197402 ..1..3..1..0....0..1..1..0....0..0..0..1....1..0..2..1....1..0..1..2 %e A197402 ..0..1..1..0....0..1..4..1....2..1..1..1....3..1..1..0....1..1..4..1 %e A197402 ..2..1..4..1....2..1..1..3....1..4..1..0....1..4..1..0....0..1..1..0 %e A197402 ..1..0..1..2....1..0..0..1....0..1..3..1....0..1..3..1....1..3..1..0 %K A197402 nonn %O A197402 1,2 %A A197402 _R. H. Hardin_ Oct 14 2011