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 A228663 #11 Sep 12 2018 07:52:05 %S A228663 8,12,140,416,2844,11148,62368,275708,1420076,6614240,32897116, %T A228663 156718796,767930400,3694025404,17985757548,86879470432,421850136604, %U A228663 2041379040012,9900460336800,47946203889788,232416817429420,1125924852017632 %N A228663 Number of 4 X n binary arrays with top left value 1 and no two ones adjacent horizontally, diagonally or antidiagonally. %H A228663 R. H. Hardin, <a href="/A228663/b228663.txt">Table of n, a(n) for n = 1..210</a> %F A228663 Empirical: a(n) = 2*a(n-1) + 16*a(n-2) - 7*a(n-3) - 18*a(n-4). %F A228663 Empirical g.f.: 4*x*(1 + x)*(2 - 3*x) / (1 - 2*x - 16*x^2 + 7*x^3 + 18*x^4). - _Colin Barker_, Sep 12 2018 %e A228663 Some solutions for n=4: %e A228663 ..1..0..0..1....1..0..1..0....1..0..0..1....1..0..0..0....1..0..0..1 %e A228663 ..0..0..0..0....0..0..0..0....1..0..0..1....0..0..1..0....0..0..0..0 %e A228663 ..0..0..0..0....1..0..0..1....0..0..0..0....0..0..0..0....0..0..0..1 %e A228663 ..0..1..0..0....1..0..0..0....0..0..0..0....1..0..0..1....1..0..0..0 %Y A228663 Row 4 of A228660. %K A228663 nonn %O A228663 1,1 %A A228663 _R. H. Hardin_, Aug 29 2013