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 A137584 #14 Apr 10 2019 13:33:08
%S A137584 0,3,6,13,30,70,163,379,881,2048,4761,11068,25730,59815,139053,323259,
%T A137584 751486,1746993,4061266,9441298,21948355,51023735,118615793,275748264,
%U A137584 641036941,1490230088,3464364646,8053670703,18722512905,43524561955,101182330758,235220381269
%N A137584 a(n) = 3*a(n-1) - 2*a(n-2) + a(n-3), n > 3.
%H A137584 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3, -2, 1).
%F A137584 G.f.: -x*(x^2-3*x+3)/(x^3-2*x^2+3*x-1).
%t A137584 LinearRecurrence[{3,-2,1},{0,3,6,13},50] (* _Harvey P. Dale_, Jan 28 2013 *)
%K A137584 nonn
%O A137584 0,2
%A A137584 _Paul Curtz_, Apr 26 2008
%E A137584 More terms from _Harvey P. Dale_, Jan 28 2013
%E A137584 a(4) = 30 inserted by _Georg Fischer_, Apr 10 2019