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 A198645 #16 Sep 08 2022 08:45:59 %S A198645 9,29,89,269,809,2429,7289,21869,65609,196829,590489,1771469,5314409, %T A198645 15943229,47829689,143489069,430467209,1291401629,3874204889, %U A198645 11622614669,34867844009,104603532029,313810596089,941431788269,2824295364809 %N A198645 a(n) = 10*3^n - 1. %H A198645 Vincenzo Librandi, <a href="/A198645/b198645.txt">Table of n, a(n) for n = 0..1000</a> %H A198645 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (4,-3). %F A198645 a(n) = 3*a(n-1) + 2, a(0)=9. %F A198645 G.f. ( 9-7*x ) / ( (3*x-1)*(x-1) ). - _R. J. Mathar_, Oct 30 2011 %t A198645 10 * 3^Range[0,30]-1 (* _Harvey P. Dale_, Feb 28 2022 *) %o A198645 (Magma) [10*3^n-1: n in [0..30]] %Y A198645 Cf. A048473. %K A198645 nonn,easy %O A198645 0,1 %A A198645 _Vincenzo Librandi_, Oct 28 2011