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 A208022 #9 Jul 22 2025 21:06:49 %S A208022 2,16,102,1377,26845,955073,56728924,5753550295,985606824420, %T A208022 287995609933240,142779868614005475,120212913507245137971, %U A208022 171965976593899860842629,417924073201539457547295084 %N A208022 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 1 0 1 vertically. %C A208022 Diagonal of A208028 %H A208022 R. H. Hardin, <a href="/A208022/b208022.txt">Table of n, a(n) for n = 1..20</a> %e A208022 Some solutions for n=4 %e A208022 ..1..0..1..1....0..1..1..0....0..1..1..0....1..0..1..1....1..0..1..0 %e A208022 ..1..0..1..0....1..1..0..0....1..0..1..0....1..0..1..0....1..0..1..1 %e A208022 ..1..1..0..0....1..1..0..1....1..0..1..1....1..1..0..0....1..1..1..1 %e A208022 ..1..1..0..1....1..1..1..1....0..1..0..1....0..1..0..1....1..1..1..1 %K A208022 nonn %O A208022 1,1 %A A208022 _R. H. Hardin_ Feb 22 2012