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 A197447 #7 Jun 02 2025 04:55:23 %S A197447 7,107,2678,52117,1108699,23829080,504568165,10724642167,228248265080, %T A197447 4853181015432,103200753393047,2194748772730124,46673287485335449, %U A197447 992547357156970890,21107504726738892508,448871249985110511395 %N A197447 Number of nX5 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,1,1,0,0 for x=0,1,2,3,4. %C A197447 Every 0 is next to 0 2's, every 1 is next to 1 1'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 A197447 Column 5 of A197450 %H A197447 R. H. Hardin, <a href="/A197447/b197447.txt">Table of n, a(n) for n = 1..210</a> %e A197447 Some solutions containing all values 0 to 4 for n=4 %e A197447 ..0..3..0..3..0....0..3..0..3..0....0..0..0..0..0....0..0..0..3..0 %e A197447 ..1..0..0..0..0....1..0..4..0..3....1..0..4..0..0....0..0..4..0..1 %e A197447 ..1..0..0..4..0....1..0..0..4..0....1..0..0..0..3....0..0..0..0..1 %e A197447 ..2..1..1..0..0....2..1..1..0..0....2..1..1..0..0....0..0..1..1..2 %K A197447 nonn %O A197447 1,1 %A A197447 _R. H. Hardin_ Oct 15 2011