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 A196487 #8 Jun 02 2025 04:25:55 %S A196487 1,1,9,99,2862,188603,28338246,10179007465,8440119388684, %T A196487 16385876855589022,74005549246712939357,780142920501811666245635 %N A196487 Number of n X n 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 2,3,0,1,4 for x=0,1,2,3,4. %C A196487 Every 0 is next to 0 2's, every 1 is next to 1 3's, every 2 is next to 2 0's, every 3 is next to 3 1's, every 4 is next to 4 4's %C A196487 Diagonal of A196493 %e A196487 Some solutions for n=4 %e A196487 ..0..1..3..1....1..1..3..1....0..0..0..0....1..3..1..0....1..3..1..0 %e A196487 ..0..0..1..0....3..1..1..1....1..1..3..1....0..1..1..0....1..1..0..1 %e A196487 ..1..3..1..0....1..0..1..3....3..1..1..0....0..1..3..1....3..1..1..3 %e A196487 ..0..1..0..0....0..0..0..1....1..0..0..0....0..0..0..0....1..0..0..1 %K A196487 nonn %O A196487 1,3 %A A196487 _R. H. Hardin_ Oct 03 2011