A092893 Smallest starting value in a Collatz '3x+1' sequence such that the sequence contains exactly n tripling steps.

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

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.

Row n=1 of A354236.

Sequence in context: A105201 A184537 A187809 * A133172 A363686 A075453

Adjacent sequences: A092890 A092891 A092892 * A092894 A092895 A092896

Keyword

nonn

Author

Hugo Pfoertner, Mar 11 2004

Status

approved