%I A006878 M4335
%S A006878 0,1,7,8,16,19,20,23,111,112,115,118,121,124,127,130,143,144,170,178,181,
%T A006878 182,208,216,237,261,267,275,278,281,307,310,323,339,350,353,374,382,385,
%U A006878 442,448,469,508,524,527,530,556,559,562,583,596,612,664,685,688,691,704
%N A006878 Record number of steps to reach 1 in `3x+1' problem, corresponding to 
               starting values in A006877.
%C A006878 Both the 3x+1 steps and the halving steps are counted.
%D A006878 B. Hayes, Computer Recreations: On the ups and downs of hailstone numbers, 
               Scientific American, 250 (No. 1, 1984), pp. 10-16.
%D A006878 D. R. Hofstadter, Goedel, Escher, Bach: an Eternal Golden Braid, Random 
               House, 1980, p. 400.
%D A006878 G. T. Leavens and M. Vermeulen, 3x+1 search problems, Computers and Mathematics 
               with Applications, 24 (1992), 79-99.
%D A006878 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A006878 T. D. Noe, <a href="b006878.txt">Table of n, a(n) for n=1..130</a> (from 
               Eric Roosendaal's data)
%H A006878 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 A006878 Eric Roosendaal, <a href="http://www.ericr.nl/wondrous/delrecs.html">
               3x+1 Delay Records</a>
%H A006878 <a href="Sindx_Go.html#GEB">Index entries for sequences from "Goedel, 
               Escher, Bach"</a>
%H A006878 <a href="Sindx_3.html#3x1">Index entries for sequences related to 3x+1 
               (or Collatz) problem</a>
%p A006878 f := proc(n) local a,L; L := 0; a := n; while a <> 1 do if a mod 2 = 
               0 then a := a/2; else a := 3*a+1; fi; L := L+1; od: RETURN(L); end;
%Y A006878 Cf. A006884, A006885, A006877, A033492, A033958, A033959.
%Y A006878 Sequence in context: A125195 A099534 A127933 this_sequence A022312 A055661 
               A054312
%Y A006878 Adjacent sequences: A006875 A006876 A006877 this_sequence A006879 A006880 
               A006881
%K A006878 nonn,nice
%O A006878 1,3
%A A006878 N. J. A. Sloane (njas(AT)research.att.com), mrob(AT)mrob.com (Robert 
               P Munafo)