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 A133423 #9 Jul 10 2015 19:57:44 %S A133423 1,5,17,23,41,53,65,71,77,95,221,317,365,383,3317,3575,3605,6473, %T A133423 24125,31901,39965,44183,163733,317885,490541,519113,558365,602591, %U A133423 707735,753023,1019615,1463897,1597973,1752575,4595735,6197855 %N A133423 Analog of A006684 for the 5x+1 problem (cf. A133419). %C A133423 The 5x+1 map sends x to x/2 if x is even, x/3 if x is divisible by 3, otherwise 5x+1. %H A133423 N. J. A. Sloane, <a href="/A133423/b133423.txt">Table of n, a(n) for n=1..89</a> (from the web page of Tomás Oliveira e Silva) %H A133423 Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/3x+1.html">The px+1 problem</a> %H A133423 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a> %Y A133423 Cf. A133419, A133424, A133419, ... %K A133423 nonn %O A133423 1,2 %A A133423 _N. J. A. Sloane_, Nov 27 2007