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 A013791 #23 Sep 08 2022 08:44:38 %S A013791 729,4782969,31381059609,205891132094649,1350851717672992089, %T A013791 8862938119652501095929,58149737003040059690390169, %U A013791 381520424476945831628649898809,2503155504993241601315571986085849,16423203268260658146231467800709255289 %N A013791 a(n) = 9^(4*n + 3). %H A013791 Vincenzo Librandi, <a href="/A013791/b013791.txt">Table of n, a(n) for n = 0..200</a> %H A013791 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A013791 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (6561). %F A013791 From _Philippe Deléham_, Dec 07 2008: (Start) %F A013791 a(n) = 6561*a(n-1); a(0)=729. %F A013791 G.f.: 729/(1-6561*x). %F A013791 a(n) = 81*A013790(n). (End) %t A013791 9^(4*Range[0,20]+3) (* or *) NestList[6561#&,729,20] (* _Harvey P. Dale_, Jul 30 2021 *) %o A013791 (Magma) [9^(4*n+3): n in [0..15]]; // _Vincenzo Librandi_, Jun 28 2011 %o A013791 (PARI) a(n)=9^(4*n+3) \\ _Charles R Greathouse IV_, Jul 11 2016 %Y A013791 Subsequence of A001019. %K A013791 nonn,easy %O A013791 0,1 %A A013791 _N. J. A. Sloane_