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 A181246 #6 Mar 26 2018 14:25:17 %S A181246 8,57,417,3032,22077,160697,1169792,8515337,61986457,451223152, %T A181246 3284626797,23910060017,174050512312,1266980540057,9222838063377, %U A181246 67136581219272,488712965249117,3557529413370537,25896623226618032 %N A181246 Number of n X 3 binary matrices with no 2 X 2 block having four 1's. %C A181246 Column 3 of A181253. %H A181246 R. H. Hardin, <a href="/A181246/b181246.txt">Table of n, a(n) for n=1..200</a> %F A181246 Empirical: a(n) = 6*a(n-1) + 10*a(n-2) - 5*a(n-3). %F A181246 Empirical g.f.: x*(8 + 9*x - 5*x^2) / (1 - 6*x - 10*x^2 + 5*x^3). - _Colin Barker_, Mar 26 2018 %Y A181246 Cf. A181253. %K A181246 nonn %O A181246 1,1 %A A181246 _R. H. Hardin_, Oct 10 2010