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 A228504 #10 Sep 12 2018 06:13:36 %S A228504 8,21,239,1252,9528,59839,413786,2724191,18387032,122539084,821945828, %T A228504 5495164996,36800032261,246231184011,1648269251345,11031030456148, %U A228504 73833534042745,494158034052549,3307432804186754,22136531409536410 %N A228504 Number of n X 6 binary arrays with top left value 1 and no two ones adjacent horizontally, vertically, diagonally or antidiagonally. %H A228504 R. H. Hardin, <a href="/A228504/b228504.txt">Table of n, a(n) for n = 1..210</a> %F A228504 Empirical: a(n) = 3*a(n-1) + 30*a(n-2) - 17*a(n-3) - 138*a(n-4) + 85*a(n-5) + 116*a(n-6) - 42*a(n-7) - 32*a(n-8). %F A228504 Empirical g.f.: x*(8 - 3*x - 64*x^2 + 41*x^3 + 63*x^4 - 24*x^5 - 18*x^6) / (1 - 3*x - 30*x^2 + 17*x^3 + 138*x^4 - 85*x^5 - 116*x^6 + 42*x^7 + 32*x^8). - _Colin Barker_, Sep 12 2018 %e A228504 Some solutions for n=4: %e A228504 ..1..0..0..1..0..0....1..0..0..0..0..0....1..0..0..1..0..1....1..0..0..1..0..0 %e A228504 ..0..0..0..0..0..1....0..0..0..0..0..1....0..0..0..0..0..0....0..0..0..0..0..1 %e A228504 ..0..1..0..0..0..0....0..0..0..0..0..0....1..0..0..0..0..0....0..0..0..1..0..0 %e A228504 ..0..0..0..0..0..0....1..0..1..0..0..1....0..0..0..0..1..0....0..1..0..0..0..0 %Y A228504 Column 6 of A228506. %K A228504 nonn %O A228504 1,1 %A A228504 _R. H. Hardin_, Aug 23 2013