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 A207945 #9 Jul 17 2025 18:57:23 %S A207945 2,16,102,1369,18172,362404,7513176,208947025,6018764552,220642515076, %T A207945 8323556149400,385679126851225,18298351908731960,1039016878950507076, %U A207945 60196918693633189580,4091835726607570472281,283040172741877232421150 %N A207945 Number of n X n 0..1 arrays avoiding 0 0 1 and 0 1 1 horizontally and 0 1 0 and 1 0 1 vertically. %C A207945 Diagonal of A207949. %H A207945 R. H. Hardin, <a href="/A207945/b207945.txt">Table of n, a(n) for n = 1..50</a> %e A207945 Some solutions for n=4 %e A207945 ..1..1..0..1....0..1..0..1....1..1..0..1....0..0..0..0....0..0..0..0 %e A207945 ..0..0..0..0....1..1..0..1....1..1..0..1....1..0..1..0....0..0..0..0 %e A207945 ..0..0..0..0....1..1..0..1....0..1..0..0....1..0..1..0....1..1..0..0 %e A207945 ..1..0..1..0....1..0..0..0....0..0..0..0....0..1..0..0....1..1..0..0 %Y A207945 Cf. A207949. %K A207945 nonn %O A207945 1,1 %A A207945 _R. H. Hardin_, Feb 21 2012