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 A195970 #8 Jun 02 2025 04:16:30 %S A195970 1,9,24,67,244,1280,5637,32909,212185,1609756,13476199,134461394 %N A195970 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 2,0,1,3,4 for x=0,1,2,3,4. %C A195970 Every 0 is next to 0 2's, every 1 is next to 1 0'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 A195970 Diagonal of A195978 %e A195970 Some solutions for n=4 %e A195970 ..1..0..0..1....1..2..2..1....1..0..1..1....1..0..1..1....1..0..0..0 %e A195970 ..1..0..0..1....0..1..1..0....1..1..1..0....2..1..1..0....2..1..1..1 %e A195970 ..1..0..0..1....0..1..1..1....0..1..1..0....2..1..1..0....2..1..1..1 %e A195970 ..1..0..0..1....1..1..0..1....0..1..1..0....1..0..1..1....1..0..0..0 %K A195970 nonn %O A195970 1,2 %A A195970 _R. H. Hardin_ Sep 25 2011