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 A231134 #10 Sep 26 2018 15:43:35 %S A231134 2,9,40,182,808,3688,16368,74728,331648,1514160,6719936,30680320, %T A231134 136161152,621652928,2758934016,12596099456,55902265856,255225567744, %U A231134 1132706802688,5171449356800,22951211032576,104785303002112 %N A231134 Number of (n+1) X (2+1) black-square subarrays of 0..2 arrays with no element equal to a strict majority of its diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order. %H A231134 R. H. Hardin, <a href="/A231134/b231134.txt">Table of n, a(n) for n = 1..210</a> %F A231134 Empirical: a(n) = 22*a(n-2) - 36*a(n-4) + 16*a(n-6). %F A231134 Empirical g.f.: x*(2 + 9*x - 4*x^2 - 16*x^3 + 8*x^5) / (1 - 22*x^2 + 36*x^4 - 16*x^6). - _Colin Barker_, Sep 26 2018 %e A231134 Some solutions for n=5: %e A231134 ..x..0..x....x..0..x....x..0..x....x..0..x....x..0..x....x..0..x....x..0..x %e A231134 ..1..x..2....1..x..0....1..x..2....1..x..1....0..x..1....0..x..1....1..x..2 %e A231134 ..x..1..x....x..2..x....x..1..x....x..2..x....x..1..x....x..2..x....x..0..x %e A231134 ..0..x..0....0..x..0....0..x..1....1..x..1....2..x..0....2..x..0....1..x..2 %e A231134 ..x..1..x....x..2..x....x..0..x....x..2..x....x..2..x....x..1..x....x..0..x %e A231134 ..2..x..0....1..x..0....2..x..2....0..x..0....0..x..0....2..x..0....2..x..2 %Y A231134 Column 2 of A231137. %K A231134 nonn %O A231134 1,1 %A A231134 _R. H. Hardin_, Nov 04 2013