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 A196139 #8 Jun 02 2025 04:17:57 %S A196139 1,5,7,83,481,2599,24615,330889,4431097,82611569,1973678929, %T A196139 55783136985 %N A196139 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 3,0,4,1,2 for x=0,1,2,3,4. %C A196139 Every 0 is next to 0 3's, every 1 is next to 1 0's, every 2 is next to 2 4's, every 3 is next to 3 1's, every 4 is next to 4 2's %C A196139 Diagonal of A196146 %e A196139 Some solutions for n=4 %e A196139 .1.3.1.0...0.1.3.1...1.3.1.0...0.0.1.1...0.1.1.0 %e A196139 .0.1.1.0...0.1.1.0...0.1.1.0...1.1.1.0...1.1.1.1 %e A196139 .1.1.1.1...0.1.1.0...0.1.1.1...3.1.1.0...1.0.0.1 %e A196139 .1.0.0.1...1.3.1.0...1.1.0.1...1.0.1.1...1.0.0.1 %K A196139 nonn %O A196139 1,2 %A A196139 _R. H. Hardin_ Sep 28 2011