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 A005032 #41 Aug 28 2023 14:29:00 %S A005032 7,21,63,189,567,1701,5103,15309,45927,137781,413343,1240029,3720087, %T A005032 11160261,33480783,100442349,301327047,903981141,2711943423, %U A005032 8135830269,24407490807,73222472421,219667417263,659002251789,1977006755367,5931020266101,17793060798303 %N A005032 a(n) = 7*3^n. %H A005032 Vincenzo Librandi, <a href="/A005032/b005032.txt">Table of n, a(n) for n = 0..1000</a> %H A005032 Milan Janjic, <a href="https://pmf.unibl.org/wp-content/uploads/2017/10/enumfun.pdf">Enumerative Formulas for Some Functions on Finite Sets</a> %H A005032 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A005032 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (3). %F A005032 From _Vincenzo Librandi_, Sep 15 2011: (Start) %F A005032 G.f.: 7/(1-3*x). %F A005032 a(n) = 3*a(n-1), a(0)=7. (End) %F A005032 E.g.f.: 7*exp(3*x). - _Stefano Spezia_, Aug 28 2023 %t A005032 7*3^Range[0, 60] (* _Vladimir Joseph Stephan Orlovsky_, Jun 09 2011 *) %t A005032 NestList[3#&,7,30] (* _Harvey P. Dale_, May 05 2016 *) %o A005032 (Magma) [7*3^n: n in [0..30]]; // _Vincenzo Librandi_, Sep 15 2011 %o A005032 (PARI) a(n)=7*3^n \\ _Charles R Greathouse IV_, Oct 07 2015 %Y A005032 Cf. A000244. %K A005032 nonn,easy %O A005032 0,1 %A A005032 _N. J. A. Sloane_