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 A207736 #9 Jul 22 2025 20:44:57 %S A207736 2,16,114,1849,86355,9259849,2215586241,1207251562500, %T A207736 1504250577851460,4240840118917220289,26956572348445823078057, %U A207736 387211891430119861291459849,12581321412478916326490284012715,923581786817019708657060682986420624 %N A207736 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 1 0 0 vertically. %C A207736 Diagonal of A207741 %H A207736 R. H. Hardin, <a href="/A207736/b207736.txt">Table of n, a(n) for n = 1..18</a> %e A207736 Some solutions for n=4 %e A207736 ..1..0..0..1....1..1..0..1....0..1..1..0....1..1..0..1....1..1..1..0 %e A207736 ..1..0..1..1....0..0..1..1....0..1..1..1....0..1..1..1....1..0..1..1 %e A207736 ..0..0..1..1....1..1..1..1....0..0..1..1....1..0..0..1....1..1..0..0 %e A207736 ..1..0..0..1....1..0..1..1....0..1..1..0....0..1..1..1....1..1..1..1 %K A207736 nonn %O A207736 1,1 %A A207736 _R. H. Hardin_ Feb 19 2012