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 A133425 #9 Jul 10 2015 19:59:18 %S A133425 1,7,11,19,31,43,163,283,403,1111,1123,1243,1303,1549,1963,4123,9643, %T A133425 10003,11539,21431,76963,97031,468109,1351963,4553323,4778471,5163139, %U A133425 6563551,7618843,45214123,65704243,161738803,202903723 %N A133425 Analog of A006684 for the 7x+1 problem (cf. A133421). %C A133425 The 7x+1 map sends x to x/2 if x is even, x/3 if x is divisible by 3, x/5 if x is divisible by 5, otherwise 7x+1. %H A133425 N. J. A. Sloane, <a href="/A133425/b133425.txt">Table of n, a(n) for n=1..53</a> (from the web page of Tomás Oliveira e Silva) %H A133425 Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/3x+1.html">The px+1 problem</a> %H A133425 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a> %Y A133425 Cf. A133421, A133426, A133419, ... %K A133425 nonn %O A133425 1,2 %A A133425 _N. J. A. Sloane_, Nov 27 2007