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 A013790 #23 Sep 08 2022 08:44:38 %S A013790 9,59049,387420489,2541865828329,16677181699666569, %T A013790 109418989131512359209,717897987691852588770249, %U A013790 4710128697246244834921603689,30903154382632612361920641803529,202755595904452569706561330872953769 %N A013790 a(n) = 9^(4*n + 1). %H A013790 Vincenzo Librandi, <a href="/A013790/b013790.txt">Table of n, a(n) for n = 0..200</a> %H A013790 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A013790 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (6561). %F A013790 From _Philippe Deléham_, Dec 07 2008: (Start) %F A013790 a(n) = 6561*a(n-1); a(0)=9. %F A013790 G.f.: 9/(1-6561*x). %F A013790 a(n) = A013791(n)/81. (End) %o A013790 (Magma) [9^(4*n+1): n in [0..15]]; // _Vincenzo Librandi_, Jun 28 2011 %o A013790 (Maxima) makelist(9^(4*n+1),n,0,20); /* _Martin Ettl_, Oct 21 2012 */ %o A013790 (PARI) a(n)=9^(4*n+1) \\ _Charles R Greathouse IV_, Jul 11 2016 %K A013790 nonn,easy %O A013790 0,1 %A A013790 _N. J. A. Sloane_