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 A013827 #24 Sep 08 2022 08:44:38 %S A013827 9,2187,531441,129140163,31381059609,7625597484987,1853020188851841, %T A013827 450283905890997363,109418989131512359209,26588814358957503287787, %U A013827 6461081889226673298932241,1570042899082081611640534563 %N A013827 a(n) = 3^(5*n + 2). %H A013827 Vincenzo Librandi, <a href="/A013827/b013827.txt">Table of n, a(n) for n = 0..200</a> %H A013827 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A013827 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (243). %F A013827 From _Philippe Deléham_, Nov 26 2008: (Start) %F A013827 a(n) = 243*a(n-1), n > 0; a(0)=9. %F A013827 G.f.: 9/(1-243*x). %F A013827 a(n) = 3*A013826(n). (End) %t A013827 3^(5*Range[0,20]+2) (* or *) NestList[243#&,9,20] (* _Harvey P. Dale_, Feb 05 2020 *) %o A013827 (Magma) [3^(5*n+2): n in [0..15]]; // _Vincenzo Librandi_, Jul 07 2011 %o A013827 (PARI) a(n)=3^(5*n+2) \\ _Charles R Greathouse IV_, Jul 11 2016 %Y A013827 Cf. A000244 (3^n), A016873 (5*n+2). %K A013827 nonn,easy %O A013827 0,1 %A A013827 _N. J. A. Sloane_