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 A155602 #27 Sep 08 2022 08:45:40
%S A155602 1,6,24,90,336,1266,4824,18570,72096,281826,1107624,4371450,17308656,
%T A155602 68703186,273218424,1088090730,4338014016,17309009346,69106897224,
%U A155602 276040168410,1102998412176,4408506864306,17623567104024,70462887356490
%N A155602 4^n + 3^n - 1.
%H A155602 Vincenzo Librandi, <a href="/A155602/b155602.txt">Table of n, a(n) for n = 0..200</a>
%H A155602 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (8,-19,12).
%F A155602 G.f.: 1/(1-4*x)+1/(1-3*x)-1/(1-x). E.g.f.: e^(4*x)+e^(3*x)-e^x.
%F A155602 a(n) = 7*a(n-1) - 12*a(n-2) -6, n>1 - _Gary Detlefs_, Jun 21 2010
%F A155602 a(n) = 8*a(n-1) - 19*a(n-2) + 12*a(n-3), n>2, a(0)=1, a(1)=6, a(2)=24. - _L. Edson Jeffery_, Oct 17 2012
%F A155602 a(n) = A074605(n)-1. - _R. J. Mathar_, Mar 10 2022
%t A155602 Table[4^n + 3^n - 1, {n, 0, 50}] (* _Vincenzo Librandi_, Oct 17 2012 *)
%t A155602 LinearRecurrence[{8,-19,12},{1,6,24},30] (* _Harvey P. Dale_, Apr 28 2018 *)
%o A155602 (Magma) [(4^n + 3^n - 1): n in [0..30]]; // _Vincenzo Librandi_, Oct 17 2012
%o A155602 (PARI) a(n)=4^n+3^n-1 \\ _Charles R Greathouse IV_, Sep 24 2015
%Y A155602 Cf. A074501, A020515, A155588, A155590, A155592-A155594, A155596-A155601.
%K A155602 nonn,easy
%O A155602 0,2
%A A155602 _Mohammad K. Azarian_, Jan 25 2009