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 A074580 #26 Sep 08 2022 08:45:07
%S A074580 3,24,194,1584,13058,108624,911234,7703664,65588738,561991824,
%T A074580 4843001474,41948320944,364990300418,3188510652624,27953062038914,
%U A074580 245823065693424,2167728096132098,19161612027339024,169737447404391554
%N A074580 a(n) = 7^n + 8^n + 9^n.
%H A074580 Vincenzo Librandi, <a href="/A074580/b074580.txt">Table of n, a(n) for n = 0..300</a>
%H A074580 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (24,-191,504).
%F A074580 From _Mohammad K. Azarian_, Dec 26 2008: (Start)
%F A074580 G.f.: 1/(1-7*x) + 1/(1-8*x) + 1/(1-9*x).
%F A074580 E.g.f.: e^(7*x) + e^(8*x) + e^(9*x). (End)
%t A074580 Table[7^n + 8^n + 9^n, {n, 0, 18}]
%t A074580 LinearRecurrence[{24,-191,504},{3,24,194},20] (* _Harvey P. Dale_, Jun 09 2019 *)
%o A074580 (Magma) [7^n + 8^n + 9^n: n in [0..20]]; // _Vincenzo Librandi_, May 20 2011
%o A074580 (PARI) a(n)=7^n+8^n+9^n \\ _Charles R Greathouse IV_, Jun 10 2011
%Y A074580 Cf. A001550, A001576, A034513, A001579, A074501-A074579.
%K A074580 easy,nonn
%O A074580 0,1
%A A074580 _Robert G. Wilson v_, Aug 23 2002