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 A196449 #8 Jun 02 2025 04:24:16 %S A196449 1,6,40,594,27320,3707781,926499600,539621963877,739769209147928 %N A196449 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 3,0,2,4,1 for x=0,1,2,3,4. %C A196449 Every 0 is next to 0 3's, every 1 is next to 1 0's, every 2 is next to 2 2's, every 3 is next to 3 4's, every 4 is next to 4 1's %C A196449 Diagonal of A196456 %e A196449 Some solutions for n=4 %e A196449 ..1..0..0..1....1..0..0..0....1..0..0..1....1..0..0..1....1..0..0..1 %e A196449 ..1..2..2..2....1..2..2..0....2..2..0..1....1..2..2..1....1..2..2..2 %e A196449 ..0..2..0..2....0..2..2..0....2..2..0..1....0..2..2..0....0..2..0..2 %e A196449 ..1..2..2..2....0..1..1..0....0..0..0..1....0..0..1..1....0..2..2..2 %K A196449 nonn %O A196449 1,2 %A A196449 _R. H. Hardin_ Oct 02 2011