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 A074552 #18 Sep 08 2022 08:45:07
%S A074552 3,15,83,495,3107,20175,134003,903855,6161987,42326415,292299923,
%T A074552 2026332015,14085959267,98111307855,684331371443,4778093436975,
%U A074552 33385561506947,233393582580495,1632228682596563,11417969833962735
%N A074552 a(n) = 3^n + 5^n + 7^n.
%H A074552 Vincenzo Librandi, <a href="/A074552/b074552.txt">Table of n, a(n) for n = 0..200</a>
%H A074552 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (15,-71,105).
%F A074552 From _Mohammad K. Azarian_, Dec 30 2008: (Start)
%F A074552 G.f.: 1/(1-3*x) + 1/(1-5*x) + 1/(1-7*x).
%F A074552 E.g.f.: exp(3*x) + exp(5*x) + exp(7*x). (End)
%F A074552 a(n) = 15*a(n-1) - 71*a(n-2) + 105*a(n-3).
%t A074552 Table[3^n + 5^n + 7^n, {n, 0, 20}]
%t A074552 LinearRecurrence[{15,-71,105},{3,15,83},20] (* _Harvey P. Dale_, Jul 16 2020 *)
%o A074552 (Magma) [3^n + 5^n + 7^n: n in [0..30]]; // _Vincenzo Librandi_, Jun 13 2011
%Y A074552 Cf. A001550, A001576, A034513, A001579, A074501 - A074580.
%K A074552 easy,nonn
%O A074552 0,1
%A A074552 _Robert G. Wilson v_, Aug 23 2002