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 A087288 #7 Feb 06 2017 13:04:05
%S A087288 4,4,10,16,34,64,130,256,514,1024,2050,4096,8194,16384,32770,65536,
%T A087288 131074,262144,524290,1048576,2097154,4194304,8388610,16777216,
%U A087288 33554434,67108864,134217730,268435456,536870914,1073741824,2147483650
%N A087288 a(n)=2a(n-1)+a(n-2)-2a(n-3).
%C A087288 a(n)=(A000051(n)-A014551(n))/2.
%H A087288 Indranil Ghosh, <a href="/A087288/b087288.txt">Table of n, a(n) for n = 0..3314</a>
%H A087288 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,1,-2).
%F A087288 G.f.: (4-4x-2x^2)/(1-2x-x^2+2x^3). a(n)=2^(n+1)+1+(-1)^n.
%t A087288 CoefficientList[Series[(4 - 4x - 2x^2)/(1 - 2x - x^2 + 2x^3), {x, 0, 30}], x]
%o A087288 (PARI) a(n)=2<<n+1+(-1)^n \\ _Charles R Greathouse IV_, Aug 20 2013
%K A087288 nonn,easy
%O A087288 0,1
%A A087288 Mario Catalani (mario.catalani(AT)unito.it), Aug 31 2003