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 A038391 #20 May 08 2016 00:48:02
%S A038391 1,4,7,13,23,33,48,69,90,118,154,190,235,290,345,411,489,567,658,763,
%T A038391 868,988,1124,1260,1413,1584,1755,1945,2155,2365,2596,2849,3102,3378,
%U A038391 3678,3978,4303,4654,5005,5383,5789,6195,6630,7095,7560,8056,8584,9112,9673
%N A038391 Expansion of (x^3+2*x+1) / ((x-1)^4*(x^2+x+1)^2).
%C A038391 Old Name was: Bisection of A028289.
%D A038391 B. N. Cyvin et al., Enumeration of conjugated hydrocarbons..., Structural Chem., 6 (1995), 85-88, equation (8).
%H A038391 Vincenzo Librandi, <a href="/A038391/b038391.txt">Table of n, a(n) for n = 0..1000</a>
%H A038391 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,2,-4,2,-1,2,-1).
%F A038391 G.f.: (x^3+2*x+1) / ((x-1)^4*(x^2+x+1)^2). - _Colin Barker_, Aug 30 2013
%F A038391 From _Wesley Ivan Hurt_, May 07 2016: (Start)
%F A038391 a(n) = 2*a(n-1)-a(n-2)+2*a(n-3)-4*a(n-4)+2*a(n-5)-a(n-6)+2*a(n-7)-a(n-8).
%F A038391 a(n) = Sum_{i=1..n+1} (1+floor((n+i+1)/3)) * (1+floor((n-i+1)/3)). (End)
%t A038391 CoefficientList[Series[(x^3 + 2 x + 1)/((x - 1)^4 (x^2 + x + 1)^2), {x, 0, 50}], x] (* _Vincenzo Librandi_, Oct 22 2013 *)
%t A038391 LinearRecurrence[{2,-1,2,-4,2,-1,2,-1},{1,4,7,13,23,33,48,69},50] (* _Harvey P. Dale_, Sep 22 2015 *)
%Y A038391 Cf. A028289.
%K A038391 nonn,easy
%O A038391 0,2
%A A038391 _N. J. A. Sloane_
%E A038391 More terms from _Colin Barker_, Aug 30 2013
%E A038391 Name changed by _Wesley Ivan Hurt_, May 07 2016