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 A208835 #9 Jul 22 2025 21:30:50 %S A208835 2,16,78,855,8736,272206,6206445,613538688,30091441770,9949962265465, %T A208835 995860712362464,1146808937112275178,223896318271083352427, %U A208835 927305041435819383020944,341298409330345173624970966 %N A208835 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 1 and 1 1 0 vertically. %C A208835 Diagonal of A208840 %H A208835 R. H. Hardin, <a href="/A208835/b208835.txt">Table of n, a(n) for n = 1..37</a> %e A208835 Some solutions for n=4 %e A208835 ..1..1..1..1....0..1..0..1....1..0..1..0....0..1..1..0....1..0..1..1 %e A208835 ..0..1..0..1....1..0..1..0....1..1..0..0....0..1..1..1....0..1..1..0 %e A208835 ..1..1..1..1....0..1..0..1....1..0..1..0....1..1..1..0....1..0..1..1 %e A208835 ..0..1..0..1....1..0..1..0....1..1..0..1....0..1..1..1....0..1..1..0 %K A208835 nonn %O A208835 1,1 %A A208835 _R. H. Hardin_ Mar 01 2012