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 A074528 #51 Sep 08 2022 08:45:07
%S A074528 3,11,49,251,1393,8051,47449,282251,1686433,10097891,60526249,
%T A074528 362976251,2177317873,13062296531,78368963449,470199366251,
%U A074528 2821153019713,16926788715971,101560344351049,609360902796251
%N A074528 a(n) = 2^n + 3^n + 6^n.
%C A074528 From _Álvar Ibeas_, Mar 24 2015: (Start)
%C A074528 Number of isomorphism classes of 3-fold coverings of a connected graph with circuit rank n+1 [Kwak and Lee].
%C A074528 Number of orbits of the conjugacy action of Sym(3) on Sym(3)^(n+1) [Kwak and Lee, 2001].
%C A074528 (End)
%D A074528 J. H. Kwak and J. Lee, Enumeration of graph coverings, surface branched coverings and related group theory, in Combinatorial and Computational Mathematics (Pohang, 2000), ed. S. Hong et al., World Scientific, Singapore 2001, pp. 97-161. [Added by _N. J. A. Sloane_, Nov 12 2009]
%H A074528 Hakan Icoz, <a href="/A074528/b074528.txt">Table of n, a(n) for n = 0..1000</a> (terms 0..200 from Vincenzo Librandi)
%H A074528 M. W. Hero and J. F. Willenbring, <a href="http://dx.doi.org/10.1016/j.disc.2009.06.021">Stable Hilbert series as related to the measurement of quantum entanglement</a>, Discrete Math., 309 (2010), 6508-6514.
%H A074528 J. H. Kwak and J. Lee, <a href="http://dx.doi.org/10.4153/CJM-1990-039-3">Isomorphism classes of graph bundles</a>. Can. J. Math., 42(4), 1990, pp. 747-761.
%H A074528 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (11,-36,36).
%F A074528 From _Mohammad K. Azarian_, Dec 26 2008: (Start)
%F A074528 G.f.: 1/(1-2*x)+1/(1-3*x)+1/(1-6*x).
%F A074528 E.g.f.: exp(2*x) + exp(3*x) + exp(6*x). (End)
%F A074528 a(n) = 11*a(n-1) - 36*a(n-2) + 36*a(n-3). - _Wesley Ivan Hurt_, Aug 21 2020
%t A074528 Table[2^n + 3^n + 6^n, {n, 0, 20}]
%t A074528 LinearRecurrence[{11,-36,36},{3,11,49},30] (* _Harvey P. Dale_, May 02 2016 *)
%o A074528 (Magma) [2^n + 3^n + 6^n: n in [0..25]]; // _Vincenzo Librandi_, Jun 11 2011
%o A074528 (PARI) a(n)=2^n+3^n+6^n \\ _Charles R Greathouse IV_, Oct 07 2015
%Y A074528 Cf. A001550, A001576, A034513, A001579, A074501-A074580.
%Y A074528 A246985 is essentially identical.
%Y A074528 Third row of A160449, shifted.
%K A074528 easy,nonn
%O A074528 0,1
%A A074528 _Robert G. Wilson v_, Aug 23 2002