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 A188560 #9 Jul 22 2025 11:15:43 %S A188560 2,16,247,13306,2109386,924245906,1199747927824,4515869742994831, %T A188560 49132225919211100127,1553292806575822383425281, %U A188560 142435222420745509758550159896,37880215295994989398957106920807127 %N A188560 Number of n X n binary arrays without the pattern 1 1 1 diagonally, vertically or horizontally. %C A188560 Diagonal of A188567 %H A188560 R. H. Hardin, <a href="/A188560/b188560.txt">Table of n, a(n) for n = 1..13</a> %e A188560 Some solutions for 3X3 %e A188560 ..0..0..0....0..0..1....0..1..1....0..1..1....0..1..0....0..1..1....0..0..1 %e A188560 ..1..0..1....0..1..0....0..1..0....1..0..0....0..1..1....0..0..0....1..0..1 %e A188560 ..1..0..1....1..0..0....0..0..0....0..1..0....0..0..0....0..0..1....1..1..0 %K A188560 nonn %O A188560 1,1 %A A188560 _R. H. Hardin_ Apr 04 2011