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 A013732 #24 Sep 08 2022 08:44:38 %S A013732 3,81,2187,59049,1594323,43046721,1162261467,31381059609,847288609443, %T A013732 22876792454961,617673396283947,16677181699666569,450283905890997363, %U A013732 12157665459056928801,328256967394537077627,8862938119652501095929 %N A013732 a(n) = 3^(3*n + 1). %H A013732 Vincenzo Librandi, <a href="/A013732/b013732.txt">Table of n, a(n) for n = 0..200</a> %H A013732 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A013732 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (27). %F A013732 From _Philippe Deléham_, Nov 25 2008: (Start) %F A013732 a(n) = 27*a(n-1); a(0)=3. %F A013732 G.f.: 3/(1-27*x). (End) %p A013732 seq(3^(3*n+1),n=0..15); # _Nathaniel Johnston_, Jun 26 2011 %t A013732 NestList[27#&,3,20] (* _Harvey P. Dale_, Apr 01 2018 *) %o A013732 (Magma) [3^(3*n+1): n in [0..25]]; // _Vincenzo Librandi_, May 25 2011 %o A013732 (PARI) a(n)=3^(3*n+1) \\ _Charles R Greathouse IV_, Jul 11 2016 %Y A013732 Cf. A013730, A013733, A013734. %K A013732 nonn,easy %O A013732 0,1 %A A013732 _N. J. A. Sloane_