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 A155597 #27 Mar 10 2022 05:24:48
%S A155597 1,5,33,209,1281,7745,46593,279809,1679361,10077185,60465153,
%T A155597 362795009,2176778241,13060685825,78364147713,470184951809,
%U A155597 2821109841921,16926659313665,101559956406273,609359739486209,3656158439014401,21936950638280705,131621703838072833
%N A155597 a(n) = 6^n - 2^n + 1.
%H A155597 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (9,-20,12).
%F A155597 G.f.: 1/(1-6*x)-1/(1-2*x)+1/(1-x).
%F A155597 E.g.f.: exp(6*x)-exp(2*x)+exp(x).
%F A155597 a(n) = 8*a(n-1)-12*a(n-2)+5 with a(0)=1, a(1)=5. - _Vincenzo Librandi_, Jul 21 2010
%F A155597 a(0)=1, a(1)=5, a(2)=33, a(n) = 9*a(n-1)-20*a(n-2)+12*a(n-3). - _Harvey P. Dale_, Jul 13 2011
%F A155597 a(n) = A248216(n)+1. - _R. J. Mathar_, Mar 10 2022
%t A155597 Table[6^n-2^n+1,{n,0,20}] (* or *) LinearRecurrence[{9,-20,12},{1,5,33},20] (* _Harvey P. Dale_, Jul 13 2011 *)
%o A155597 (PARI) a(n) = 6^n-2^n+1 \\ _Charles R Greathouse IV_, Jul 25 2011
%Y A155597 Cf. A074501, A020515, A155588, A155590, A155592, A155593, A155594, A155596.
%K A155597 nonn,easy
%O A155597 0,2
%A A155597 _Mohammad K. Azarian_, Jan 25 2009