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 A196140 #7 Jun 02 2025 04:18:02 %S A196140 3,5,8,17,34,62,123,243,471,924,1817,3558,6978,13697,26865,52699, %T A196140 103398,202847,397944,780720,1531657,3004865,5895113,11565346, %U A196140 22689467,44513380,87328672,171325871,336115955,659409701,1293664016,2537976953,4979134498 %N A196140 Number of nX2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 3,0,4,1,2 for x=0,1,2,3,4. %C A196140 Every 0 is next to 0 3's, every 1 is next to 1 0's, every 2 is next to 2 4's, every 3 is next to 3 1's, every 4 is next to 4 2's %C A196140 Column 2 of A196146 %H A196140 R. H. Hardin, <a href="/A196140/b196140.txt">Table of n, a(n) for n = 1..200</a> %F A196140 Empirical: a(n) = 2*a(n-1) +a(n-3) -2*a(n-4) -a(n-5) +a(n-6) %e A196140 Some solutions for n=4 %e A196140 .1.0...0.1...1.0...0.0...0.1...1.0...1.0...1.0...0.0...1.1 %e A196140 .1.0...1.3...3.1...0.0...0.1...1.1...1.0...3.1...1.1...0.0 %e A196140 .1.1...3.1...1.1...0.0...1.1...0.1...1.0...1.3...1.1...0.0 %e A196140 .0.1...1.0...0.0...1.1...1.0...0.1...1.0...0.1...0.0...0.0 %K A196140 nonn %O A196140 1,1 %A A196140 _R. H. Hardin_ Sep 28 2011