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 A207595 #9 Jul 22 2025 20:37:37 %S A207595 2,16,90,441,3915,42025,292600,1982464,21925800,268730449,2281109103, %T A207595 19215781641,242188032450,3266593546384,32361595709850, %U A207595 320442399819025,4434278073813775,64468102969055809,723471023371037040 %N A207595 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 1 0 1 vertically. %C A207595 Diagonal of A207599 %H A207595 R. H. Hardin, <a href="/A207595/b207595.txt">Table of n, a(n) for n = 1..64</a> %e A207595 Some solutions for n=4 %e A207595 ..1..1..1..1....1..0..0..1....1..1..0..1....1..0..0..1....1..0..1..1 %e A207595 ..1..1..1..0....0..1..1..0....1..0..1..1....1..0..1..1....0..0..1..1 %e A207595 ..1..1..1..0....0..1..1..0....0..0..1..1....0..0..1..1....0..0..1..1 %e A207595 ..1..1..0..0....0..1..1..0....0..0..1..1....0..0..1..1....0..0..1..1 %K A207595 nonn %O A207595 1,1 %A A207595 _R. H. Hardin_ Feb 19 2012