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 A196131 #8 Jun 02 2025 04:17:22 %S A196131 1,4,4,31,326,3716,75720,2040678,86632050,5257705657 %N A196131 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 0,2,1,3,4 for x=0,1,2,3,4. %C A196131 Every 0 is next to 0 0's, every 1 is next to 1 2's, every 2 is next to 2 1's, every 3 is next to 3 3's, every 4 is next to 4 4's %C A196131 Diagonal of A196138 %e A196131 Some solutions for n=4 %e A196131 ..0..2..1..0....1..0..1..2....0..1..2..0....0..2..1..0....1..1..2..0 %e A196131 ..1..1..1..2....2..1..0..1....2..1..1..1....1..1..1..2....2..0..1..1 %e A196131 ..2..1..0..1....2..1..1..0....1..1..0..2....2..1..1..1....1..1..1..2 %e A196131 ..0..1..2..1....1..0..2..1....0..2..1..1....0..1..2..0....0..2..1..0 %K A196131 nonn %O A196131 1,2 %A A196131 _R. H. Hardin_ Sep 28 2011