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 A196951 #8 Jun 02 2025 04:38:37 %S A196951 1,5,26,492,23956,3166711,1147966466,1139814557483,3088781045935076, %T A196951 22873717950695283084,463109589156291297397232, %U A196951 25624345402722028725104412700,3874850344967499961830383314013710 %N A196951 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 2,1,3,4,0 for x=0,1,2,3,4. %C A196951 Every 0 is next to 0 2's, every 1 is next to 1 1's, every 2 is next to 2 3's, every 3 is next to 3 4's, every 4 is next to 4 0's %C A196951 Diagonal of A196957 %e A196951 Some solutions for n=4 %e A196951 ..0..0..1..1....0..1..0..0....1..1..0..0....1..1..0..1....1..0..0..0 %e A196951 ..0..0..0..0....0..1..0..1....0..0..4..0....0..0..0..1....1..0..1..1 %e A196951 ..1..0..0..1....0..0..0..1....1..1..0..0....0..0..4..0....0..0..0..0 %e A196951 ..1..0..0..1....0..0..0..0....0..0..0..0....1..1..0..0....0..1..1..0 %K A196951 nonn %O A196951 1,2 %A A196951 _R. H. Hardin_ Oct 08 2011