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 A208033 #9 Jul 22 2025 21:07:38 %S A208033 2,16,102,961,21147,811801,44918280,4186478209,714320063886, %T A208033 207770920176121,99259943862610227,80457895275392565121, %U A208033 112399424925446158169479,266845510437068945897046016 %N A208033 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 0 and 1 0 1 vertically. %C A208033 Diagonal of A208039 %H A208033 R. H. Hardin, <a href="/A208033/b208033.txt">Table of n, a(n) for n = 1..20</a> %e A208033 Some solutions for n=4 %e A208033 ..1..1..1..1....1..0..0..1....1..1..1..1....1..0..0..1....1..0..0..1 %e A208033 ..0..0..1..1....1..0..1..1....1..1..1..1....0..0..1..1....0..1..1..0 %e A208033 ..0..0..1..1....0..1..1..1....1..1..1..1....0..1..1..1....0..1..1..0 %e A208033 ..1..1..1..0....0..0..1..1....0..1..1..1....1..0..0..1....1..1..1..1 %K A208033 nonn %O A208033 1,1 %A A208033 _R. H. Hardin_ Feb 22 2012