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 A197665 #8 Jun 02 2025 05:04:22 %S A197665 1,9,95,5005,709083,311676959,417293944115,1717065757366333 %N A197665 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 4,0,1,0,1 for x=0,1,2,3,4. %C A197665 Every 0 is next to 0 4's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 0's, every 4 is next to 4 1's %C A197665 Diagonal of A197672 %e A197665 Some solutions for n=4 %e A197665 ..2..1..1..1....1..0..0..0....0..1..2..0....0..0..3..0....0..1..2..0 %e A197665 ..1..0..0..0....2..0..3..0....1..4..1..0....0..0..0..3....0..1..1..0 %e A197665 ..1..0..0..3....1..1..2..0....1..1..1..0....0..0..3..0....1..1..2..0 %e A197665 ..1..0..3..0....0..2..1..0....0..0..2..1....1..1..2..1....1..0..0..0 %K A197665 nonn %O A197665 1,2 %A A197665 _R. H. Hardin_ Oct 17 2011