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 A155614 #18 Oct 07 2015 15:08:38
%S A155614 1,7,73,703,6481,58807,530713,4780783,43040161,387400807,3486725353,
%T A155614 31380882463,282429005041,2541864234007,22876787671993,
%U A155614 205891117745743,1853020145805121,16677181570526407,150094634909578633
%N A155614 9^n - 3^n + 1.
%H A155614 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (13,-39,27).
%F A155614 G.f.: 1/(1-9*x)-1/(1-3*x)+1/(1-x).
%F A155614 E.g.f.: e^(9*x)-e^(3*x)+e^x.
%F A155614 a(n) = 12*a(n-1)-27*a(n-2)+16 with a(0)=1, a(1)=7. - _Vincenzo Librandi_, Jul 21 2010
%t A155614 Table[9^n-3^n+1,{n,0,20}] (* _Harvey P. Dale_, Feb 03 2011 *)
%o A155614 (PARI) a(n)=9^n-3^n+1 \\ _Charles R Greathouse IV_, Oct 07 2015
%Y A155614 Cf. A155599, A155600, A155601, A155602, A155603, A155604, A155605, A155606, A155607, A155608, A155609, A155610, A155611, A155612, A155613.
%K A155614 nonn,easy
%O A155614 0,2
%A A155614 _Mohammad K. Azarian_, Jan 26 2009