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 A155620 #12 Jun 13 2015 00:52:47
%S A155620 1,12,96,792,6816,60072,535536,4799352,43112256,387682632,3487832976,
%T A155620 31385253912,282446313696,2541932937192,22877060890416,
%U A155620 205892205836472,1853024483819136,16677198879535752,150094704016475856
%N A155620 9^n+4^n-1.
%H A155620 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (14,-49,36).
%F A155620 G.f.: 1/(1-9*x)+1/(1-4*x)-1/(1-x). E.g.f.: e^(9*x)+e^(4*x)-e^x.
%F A155620 a(n)=13*a(n-1)-36*a(n-2)-24 with a(0)=1, a(1)=12 [From _Vincenzo Librandi_, Jul 21 2010]
%F A155620 a(0)=1, a(1)=12, a(2)=96, a(n)=14*a(n-1)-49*a(n-2)+36*a(n-3). - _Harvey P. Dale_, Feb 02 2015
%t A155620 LinearRecurrence[{14,-49,36},{1,12,96},30] (* _Harvey P. Dale_, Feb 02 2015 *)
%Y A155620 A155588, A155599, A155607 - A155619.
%K A155620 nonn,easy
%O A155620 0,2
%A A155620 _Mohammad K. Azarian_, Jan 27 2009