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 A074543 #18 Sep 08 2022 08:45:07
%S A074543 3,17,121,953,7873,66857,578161,5063033,44726593,397498697,3547251601,
%T A074543 31743858713,284606322913,2554926530537,22955156635441,
%U A074543 206361317111993,1855841298824833,16694108359242377,150196195253929681
%N A074543 a(n) = 2^n + 6^n + 9^n.
%H A074543 Vincenzo Librandi, <a href="/A074543/b074543.txt">Table of n, a(n) for n = 0..200</a>
%H A074543 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (17,-84,108).
%F A074543 From _Mohammad K. Azarian_, Dec 27 2008: (Start)
%F A074543 G.f.: 1/(1-2*x) + 1/(1-6*x) + 1/(1-9*x).
%F A074543 E.g.f.: exp(2*x) + exp(6*x) + exp(9*x). (End)
%F A074543 a(n) = 17*a(n-1) - 84*a(n-2) + 108*a(n-3); a(0)=3, a(1)=17, a(2)=121. - _Harvey P. Dale_, Feb 20 2015
%t A074543 Table[2^n + 6^n + 9^n, {n, 0, 20}]
%t A074543 LinearRecurrence[{17,-84,108},{3,17,121},30] (* _Harvey P. Dale_, Feb 20 2015 *)
%o A074543 (Magma) [2^n + 6^n + 9^n: n in [0..20]]; // _Vincenzo Librandi_, Jun 11 2011
%Y A074543 Cf. A001550, A001576, A034513, A001579, A074501 - A074580.
%K A074543 easy,nonn
%O A074543 0,1
%A A074543 _Robert G. Wilson v_, Aug 23 2002