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 A074534 #16 Sep 08 2022 08:45:07
%S A074534 3,13,69,415,2673,17863,121809,840055,5830593,40616263,283524849,
%T A074534 1981523095,13858068513,96956127463,678491524689,4748635284535,
%U A074534 33237225602433,232647693987463,1628482317649329,11399170063804375
%N A074534 a(n) = 2^n + 4^n + 7^n.
%H A074534 Vincenzo Librandi, <a href="/A074534/b074534.txt">Table of n, a(n) for n = 0..200</a>
%H A074534 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (13,-50,56).
%F A074534 From _Mohammad K. Azarian_, Dec 27 2008: (Start)
%F A074534 G.f.: 1/(1-2*x) + 1/(1-4*x) + 1/(1-7*x).
%F A074534 E.g.f.: exp(2*x) + exp(4*x) + exp(7*x). (End)
%t A074534 Table[2^n + 4^n + 7^n, {n, 0, 20}]
%o A074534 (Magma) [2^n + 4^n + 7^n: n in [0..25]]; // _Vincenzo Librandi_, Jun 11 2011
%Y A074534 Cf. A001550, A001576, A034513, A001579, A074501 - A074580.
%K A074534 easy,nonn
%O A074534 0,1
%A A074534 _Robert G. Wilson v_, Aug 23 2002