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 A006513 M0189 #24 Jul 08 2025 16:48:37 %S A006513 1,2,2,1,1,1,2,2,2,2,1,2,2,1,1,1,2,1,1,1,1,2,2,1,1,1,1,2,2,2,2,2,1,1, %T A006513 1,2,2,2,2,2,2,2,1,1,1,1,1,2,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,2,2,2,2, %U A006513 2,2,2,1,2,1,2,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,1,2,1,1,1,1,1,1,1,1,1,1,1,1 %N A006513 Limit of the image of n after 2k iterates of `(3x+1)/2' map as k grows. %C A006513 The map is x -> (3x+1)/2 for odd x, and x -> x/2 for even x. %D A006513 R. K. Guy, Unsolved Problems in Number Theory, E16. %D A006513 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006513 J. C. Lagarias, <a href="http://www.cecm.sfu.ca/organics/papers/lagarias/paper/html/paper.html">The 3x+1 problem and its generalizations</a>, Amer. Math. Monthly, 92 (1985), 3-23. %H A006513 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a> %o A006513 (PARI) f(n) = if (n%2, (3*n+1)/2, n/2); \\ A014682 %o A006513 a(n) = my(last = n); while (1, my(new = f(f(last))); if (new == last, return(new)); last = new;); \\ _Michel Marcus_, Feb 03 2022 %Y A006513 Cf. A014682. %K A006513 nonn %O A006513 1,2 %A A006513 _N. J. A. Sloane_ %E A006513 More terms from _Max Alekseyev_, Oct 14 2012