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 A074554 #20 Sep 08 2022 08:45:07
%S A074554 3,17,115,881,7267,62417,547795,4863281,43443907,389393297,3496609075,
%T A074554 31430064881,282674208547,2543088125777,22882900753555,
%U A074554 205921664021681,1853172819789187,16677944768259857,150098450381685235
%N A074554 a(n) = 3^n + 5^n + 9^n.
%H A074554 Vincenzo Librandi, <a href="/A074554/b074554.txt">Table of n, a(n) for n = 0..200</a>
%H A074554 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (17,-87,135).
%F A074554 From _Mohammad K. Azarian_, Dec 30 2008: (Start)
%F A074554 G.f.: 1/(1-3*x) + 1/(1-5*x) + 1/(1-9*x).
%F A074554 E.g.f.: exp(3*x) + exp(5*x) + exp(9*x). (End)
%F A074554 a(n) = 17*a(n-1) - 87*a(n-2) + 135*a(n-3).
%t A074554 Table[3^n + 5^n + 9^n, {n, 0, 20}]
%t A074554 LinearRecurrence[{17,-87,135},{3,17,115},30] (* _Harvey P. Dale_, Nov 27 2012 *)
%o A074554 (Magma) [3^n + 5^n + 9^n: n in [0..30]]; // _Vincenzo Librandi_, Jun 13 2011
%Y A074554 Cf. A001550, A001576, A034513, A001579, A074501 - A074580.
%K A074554 easy,nonn
%O A074554 0,1
%A A074554 _Robert G. Wilson v_, Aug 23 2002