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 A068928 #9 Oct 17 2019 11:40:58 %S A068928 2,2,2,4,5,9,12,21,30,51,76,127,195,322,504,826,1309,2135,3410,5545, %T A068928 8900,14445,23256,37701,60813,98514,159094,257608,416325,673933, %U A068928 1089648,1763581,2852242,4615823,7466468,12082291,19546175,31628466 %N A068928 Number of incongruent ways to tile a 3 X 2n room with 1x2 Tatami mats. At most 3 Tatami mats may meet at a point. %H A068928 R. J. Mathar, <a href="http://arxiv.org/abs/1311.6135">Paving rectangular regions with rectangular tiles,....</a>, arXiv:1311.6135 [math.CO], Table 10. %H A068928 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-1,0,-1,-1). %F A068928 For n >= 8, a(n) = a(n-1) + 2*a(n-2) - a(n-3) - a(n-5) - a(n-6). %F A068928 O.g.f.: x(2-4x^2-x^4+x^6)/((1-x-x^2)(1-x^2-x^4)). a(n) = (A000045(n+1)+A053602(n+1))/2, n>1. [From _R. J. Mathar_, Aug 30 2008] %Y A068928 Cf. A068922 for total number of tilings, A068926 for more info. %Y A068928 Essentially the same as A001224. %K A068928 easy,nonn %O A068928 1,1 %A A068928 _Dean Hickerson_, Mar 11 2002