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 A199644 #7 Jul 22 2025 13:21:07 %S A199644 3,288,12748,658770,32177372,1614250077,80053957248,3988024796446, %T A199644 198328767139736,9869645990489747,491026123739354858, %U A199644 24431608808618462704,1215575822472077464282,60480991464785183388557 %N A199644 Number of nX5 0..2 arrays with values 0..2 introduced in row major order and each element equal to one or two horizontal and vertical neighbors. %C A199644 Column 5 of A199647 %H A199644 R. H. Hardin, <a href="/A199644/b199644.txt">Table of n, a(n) for n = 1..177</a> %e A199644 Some solutions for n=3 %e A199644 ..0..1..0..2..2....0..0..0..0..0....0..0..0..1..1....0..1..0..0..1 %e A199644 ..0..1..0..2..2....0..1..1..2..1....0..1..1..1..2....0..1..1..0..1 %e A199644 ..0..2..2..0..0....0..1..1..2..1....0..0..0..2..2....2..2..1..0..1 %K A199644 nonn %O A199644 1,1 %A A199644 _R. H. Hardin_ Nov 08 2011