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 A207508 #9 Jun 18 2022 17:45:44 %S A207508 2,16,72,438,2638,10340,50322,221672,938572,4001444,16081184,65882872, %T A207508 265536422,1041167756,4136910380,16075083164,62441083194,240925209706, %U A207508 924668629616,3528820338804,13446998876758,50858295309890 %N A207508 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 1 1 vertically. %C A207508 Diagonal of A207514. %H A207508 R. H. Hardin, <a href="/A207508/b207508.txt">Table of n, a(n) for n = 1..24</a> %e A207508 Some solutions for n=4 %e A207508 ..1..1..0..1....1..0..1..0....0..1..0..0....1..1..0..1....1..0..0..1 %e A207508 ..1..1..1..1....0..1..0..1....0..0..1..0....1..0..1..0....1..1..0..1 %e A207508 ..0..0..1..0....1..0..1..0....0..1..0..0....0..1..0..0....0..1..0..0 %e A207508 ..0..1..0..0....1..1..0..1....0..1..0..0....0..0..1..0....1..0..0..1 %Y A207508 Cf. A207514. %K A207508 nonn %O A207508 1,1 %A A207508 _R. H. Hardin_, Feb 18 2012