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 A118535 #10 Aug 14 2020 13:00:51 %S A118535 1,21,32,43,54,65,76,87,98,109,921,149,961,189,1001,1021,1221,1241, %T A118535 1441,1461,1661,1681,1881,1901,1111,1131,1331,1351,1551,1571,1771, %U A118535 1791,1991,2011,1122,2231,1342,2451,1562,2671,1782,2891,2002,2022 %N A118535 Start with 1 and repeatedly reverse the digits and add 20 to get the next term. %H A118535 Harvey P. Dale, <a href="/A118535/b118535.txt">Table of n, a(n) for n = 1..1000</a> %H A118535 N. J. A. Sloane and others, <a href="/wiki/Sequences_of_RADD_type">Sequences of RADD type</a>, OEIS wiki. %F A118535 Never reaches a cycle (see A117816). %t A118535 NestList[IntegerReverse[#]+20&,1,50] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Aug 14 2020 *) %K A118535 nonn,base %O A118535 1,2 %A A118535 _N. J. A. Sloane_, May 07 2006