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 A198698 #22 Jun 14 2025 10:38:05 %S A198698 2,29,299,2999,29999,299999,2999999,29999999,299999999,2999999999, %T A198698 29999999999,299999999999,2999999999999,29999999999999, %U A198698 299999999999999,2999999999999999,29999999999999999,299999999999999999,2999999999999999999,29999999999999999999,299999999999999999999 %N A198698 a(n) = 3*10^n - 1. %H A198698 Vincenzo Librandi, <a href="/A198698/b198698.txt">Table of n, a(n) for n = 0..200</a> %H A198698 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10). %F A198698 a(n) = 10*a(n-1) + 9, a(0)=2. %F A198698 a(n) = 11*a(n-1) - 10*a(n-2), n>1. %F A198698 G.f.: (2+7*x)/((10*x-1)*(x-1)). - _R. J. Mathar_, Oct 30 2011 %F A198698 E.g.f.: exp(x)*(3*exp(9*x) - 1). - _Elmo R. Oliveira_, Jun 13 2025 %o A198698 (Magma) [3*10^n-1: n in [0..30]]; %Y A198698 Cf. A002283, A109002. %K A198698 nonn,easy %O A198698 0,1 %A A198698 _Vincenzo Librandi_, Oct 29 2011