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A092893 Smallest starting value in a Collatz '3x+1' sequence such that the sequence contains exactly n tripling steps. 6
1, 5, 3, 17, 11, 7, 9, 25, 33, 43, 57, 39, 105, 135, 185, 123, 169, 219, 159, 379, 283, 377, 251, 167, 111, 297, 395, 263, 175, 233, 155, 103, 137, 91, 121, 161, 107, 71, 47, 31, 41, 27, 73, 97, 129, 171, 231, 313, 411, 543, 731, 487, 327, 859, 1145, 763, 1017, 1351 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

First occurrence of n in A006667.

These are the odd (primitive) terms in A129304. - T. D. Noe, Apr 09 2007

LINKS

T. D. Noe, Table of n, a(n) for n=0..300

Jeffrey R. Goodwin, The 3x+1 Problem and Integer Representations, Arxiv preprint arXiv:1504.03040 [math.NT], 2015.

Eric Weisstein's World of Mathematics, Collatz Problem

Index entries for sequences related to 3x+1 (or Collatz) problem

EXAMPLE

a(4)=11 because the Collatz sequence 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1 is the first sequence containing 4 tripling steps.

MATHEMATICA

a[n_]:=Length[Select[NestWhileList[If[EvenQ[#], #/2, 3#+1] &, n, #>1 &], OddQ]]; Table[i=1; While[a[i]!=n, i=i+2]; i, {n, 58}] (* Jayanta Basu, May 27 2013 *)

CROSSREFS

Cf. A006667, A092892, A087228.

Sequence in context: A105201 A184537 A187809 * A133172 A075453 A073845

Adjacent sequences:  A092890 A092891 A092892 * A092894 A092895 A092896

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, Mar 11 2004

STATUS

approved

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Last modified June 16 21:55 EDT 2021. Contains 345080 sequences. (Running on oeis4.)