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 A198178 #8 Jun 02 2025 05:23:47 %S A198178 1,4,9,59,2033,51688,4522496,559601114,174674654015 %N A198178 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 0,2,1,0,0 for x=0,1,2,3,4. %C A198178 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 0's, every 4 is next to 4 0's %C A198178 Diagonal of A198185 %e A198178 Some solutions for n=4 %e A198178 ..0..2..1..1....0..3..0..1....1..0..3..0....1..0..2..1....1..0..1..2 %e A198178 ..1..1..0..2....1..0..3..2....2..3..0..1....2..1..1..0....2..1..0..1 %e A198178 ..2..0..1..1....2..1..0..1....1..0..1..2....2..1..0..1....0..1..1..0 %e A198178 ..1..1..2..0....0..1..2..1....1..2..1..0....1..0..1..2....1..2..2..1 %K A198178 nonn %O A198178 1,2 %A A198178 _R. H. Hardin_ Oct 21 2011