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 A226509 #11 Mar 15 2016 09:20:50
%S A226509 3,3,3,8,9,12,16,23,29,41,56,79,110,158,225,325,469,682,991,1446,2110,
%T A226509 3085,4511,6603,9666,14157,20736,30380,44511,65223,95575,140060,
%U A226509 205253,300800,440828,646051,946817,1387613,2033628,2980411
%N A226509 Expansion of (3-2*x)/(1-x-x^3)+x/(1-x)^2+x/(1-x^2).
%D A226509 Z. Skupien, Sums of Powered Characteristic Roots Count Distance-Independent Circular Sets, Discussiones Mathematicae Graph Theory. Volume 33, Issue 1, Pages 217-229, ISSN (Print) 2083-5892, DOI: 10.7151/dmgt.1658, April 2013.
%H A226509 Vincenzo Librandi, <a href="/A226509/b226509.txt">Table of n, a(n) for n = 0..1000</a>
%H A226509 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-1,0,-1,1).
%F A226509 a(n) = A137726(n), for n>2 and a(0) = a(1) = a(2) = 3. [_Bruno Berselli_, Jun 17 2013]
%t A226509 CoefficientList[Series[(3 - 2 x) / (1 - x - x^3) + x / (1 - x)^2 + x / (1 - x^2), {x, 0, 40}], x] (* _Vincenzo Librandi_, Jun 19 2013 *)
%K A226509 nonn,easy
%O A226509 0,1
%A A226509 _N. J. A. Sloane_, Jun 11 2013