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 A207768 #9 Jul 22 2025 20:49:24 %S A207768 2,16,84,828,11950,195160,6513576,364308938,15284596082,2700018736020, %T A207768 787454317079753,72216754252055376,73270546375550142283, %U A207768 119728540088330705652453,22114539991379386419299095 %N A207768 Number of n X n 0..1 arrays avoiding 0 0 0 and 1 1 1 horizontally and 0 0 1 and 0 1 0 vertically. %C A207768 Diagonal of A207774 %H A207768 R. H. Hardin, <a href="/A207768/b207768.txt">Table of n, a(n) for n = 1..18</a> %e A207768 Some solutions for n=4 %e A207768 ..1..1..0..0....1..1..0..1....0..1..1..0....1..0..0..1....1..1..0..0 %e A207768 ..0..1..0..1....1..1..0..1....1..1..0..0....1..0..1..1....1..0..1..0 %e A207768 ..1..1..0..1....1..1..0..1....1..0..1..0....0..0..1..1....1..0..1..0 %e A207768 ..1..1..0..0....0..1..0..1....0..1..1..0....0..0..1..0....1..0..1..0 %K A207768 nonn %O A207768 1,1 %A A207768 _R. H. Hardin_ Feb 20 2012