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 A199559 #10 Sep 08 2022 08:46:00 %S A199559 3,19,163,1459,13123,118099,1062883,9565939,86093443,774840979, %T A199559 6973568803,62762119219,564859072963,5083731656659,45753584909923, %U A199559 411782264189299,3706040377703683,33354363399333139,300189270593998243 %N A199559 2*9^n+1. %H A199559 Vincenzo Librandi, <a href="/A199559/b199559.txt">Table of n, a(n) for n = 0..1000</a> %H A199559 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (10,-9). %F A199559 a(n) = 9*a(n-1)-8. %F A199559 a(n) = 10*a(n-1)-9*a(n-2). %F A199559 G.f.: (3-11*x)/((1-x)*(1-9*x)). %o A199559 (Magma) [2*9^n+1: n in [0..30]]; %K A199559 nonn,easy %O A199559 0,1 %A A199559 _Vincenzo Librandi_, Nov 08 2011