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 A197449 #7 Jun 02 2025 04:55:33 %S A197449 16,957,88767,6455759,504568165,40087361395,3148323076125, %T A197449 247785141871837,19514460176530843,1536223846055481075, %U A197449 120945067934443941208,9522042330180130196817,749659600975504964938552 %N A197449 Number of nX7 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 A197449 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 A197449 Column 7 of A197450 %H A197449 R. H. Hardin, <a href="/A197449/b197449.txt">Table of n, a(n) for n = 1..158</a> %e A197449 Some solutions containing all values 0 to 4 for n=4 %e A197449 ..0..0..3..0..0..3..0....0..0..3..0..0..0..0....0..0..0..0..1..1..0 %e A197449 ..0..3..0..0..4..0..1....1..0..0..4..0..3..1....1..3..0..4..0..0..1 %e A197449 ..0..3..0..0..0..0..1....1..0..3..0..0..0..1....1..0..0..0..3..0..1 %e A197449 ..0..0..3..0..1..1..2....2..1..1..0..3..0..0....0..0..3..0..1..1..2 %K A197449 nonn %O A197449 1,1 %A A197449 _R. H. Hardin_ Oct 15 2011