

A092892


Smallest starting value in a Collatz '3x+1' sequence such that the sequence contains exactly n halving steps.


7



1, 2, 4, 8, 5, 3, 6, 12, 24, 17, 11, 7, 14, 9, 18, 36, 25, 49, 33, 65, 43, 86, 57, 39, 78, 153, 105, 203, 135, 270, 185, 123, 246, 169, 329, 219, 159, 295, 569, 379, 283, 505, 377, 251, 167, 111, 222, 444, 297, 593, 395, 263, 175, 350, 233, 155, 103, 206, 137, 91, 182
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OFFSET

0,2


COMMENTS

First occurrence of n in A006666.
The graph of this sequence has features similar to those of A092893, but with the xaxis scaled by log(3)/log(2).  T. D. Noe, Apr 09 2007


LINKS

T. D. Noe, Table of n, a(n) for n=0..500
Eric Weisstein's World of Mathematics, Collatz Problem.
Index entries for sequences related to 3x+1 (or Collatz) problem


EXAMPLE

a(5)=3 because the Collatz sequence 3,10,5,16,8,4,2,1 is the first sequence containing 5 halving steps.


MATHEMATICA

coll[n_]:= NestWhileList[If[EvenQ[#], #/2, 3#+1] &, n, #>1 &]; Table[i = 1; While[Count[coll[i], _?EvenQ] != n, i++]; i, {n, 0, 60}] (* Jayanta Basu, Jun 05 2013 *)


PROG

(Haskell)
import Data.List (elemIndex); import Data.Maybe (fromJust)
a092892 = (+ 1) . fromJust . (`elemIndex` a006666_list)
 Reinhard Zumkeller, Mar 14 2014


CROSSREFS

Cf. A006666, A092893.
Sequence in context: A273170 A135447 A163339 * A146079 A165669 A227818
Adjacent sequences: A092889 A092890 A092891 * A092893 A092894 A092895


KEYWORD

nonn,look


AUTHOR

Hugo Pfoertner, Mar 11 2004


STATUS

approved



