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 A208073 #9 Jul 22 2025 21:09:03 %S A208073 2,16,126,2601,139605,17098225,4412968520,2580469555456, %T A208073 3485691022698248,10640054910525548209,72722981173167013234455, %U A208073 1123008691175260414001447481,39309117808240836879763740048294 %N A208073 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 0 1 0 vertically. %C A208073 Diagonal of A208078 %H A208073 R. H. Hardin, <a href="/A208073/b208073.txt">Table of n, a(n) for n = 1..22</a> %e A208073 Some solutions for n=4 %e A208073 ..1..0..1..0....1..0..1..0....0..1..0..0....1..0..1..0....1..0..1..1 %e A208073 ..1..0..1..1....1..1..0..1....0..1..1..0....0..1..0..0....0..1..1..1 %e A208073 ..0..1..0..1....0..1..1..1....1..1..1..1....1..1..1..1....0..1..1..1 %e A208073 ..1..1..1..0....1..1..1..1....1..0..1..1....1..1..1..1....1..0..1..0 %K A208073 nonn %O A208073 1,1 %A A208073 _R. H. Hardin_ Feb 23 2012