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 A181247 #6 Mar 26 2018 14:16:59 %S A181247 16,216,3032,42176,587920,8191392,114142368,1590466304,22161786304, %T A181247 308805072256,4302929532288,59957567962112,835456401197312, %U A181247 11641356029819392,162212139560176128,2260284639281590272 %N A181247 Number of n X 4 binary matrices with no 2 X 2 block having four 1's. %C A181247 Column 4 of A181253. %H A181247 R. H. Hardin, <a href="/A181247/b181247.txt">Table of n, a(n) for n=1..200</a> %F A181247 Empirical: a(n) = 10*a(n-1) + 54*a(n-2) + 16*a(n-3) - 64*a(n-4). %F A181247 Empirical g.f.: 8*x*(2 + 7*x + x^2 - 8*x^3) / (1 - 10*x - 54*x^2 - 16*x^3 + 64*x^4). - _Colin Barker_, Mar 26 2018 %Y A181247 Cf. A181253. %K A181247 nonn %O A181247 1,1 %A A181247 _R. H. Hardin_, Oct 10 2010