A039500 Iterations of "k->k/2 if k is even, k->3k-1 if k is odd" (A001281) starting at these numbers reach 1.

1, 2, 3, 4, 6, 8, 11, 12, 15, 16, 22, 24, 29, 30, 32, 39, 43, 44, 48, 53, 57, 58, 59, 60, 64, 65, 69, 71, 77, 78, 79, 85, 86, 87, 88, 95, 96, 97, 101, 103, 105, 106, 113, 114, 115, 116, 118, 120, 127, 128, 129, 130, 135, 137, 138, 141, 142, 145, 151, 154, 155, 156

Offset

1,2

Comments

It appears that lim_{n->oo} a(n)/n = 5/2. - Benoit Cloitre, Jan 29 2006

Equivalent to the Collatz ('3n+1') problem for negative integers. - Dmitry Kamenetsky, Jan 12 2017

There are 327679 terms in this sequence which are less than 1000000. Based on this, I would suggest that the limit of a(n)/n is more likely to be 3 than 5/2. This is also a natural guess; there are three known periodic orbits for this recurrence. - David Speyer, Mar 25 2022

Links

Alois P. Heinz, Table of n, a(n) for n = 1..20000

Mathematica

colln[n_]:= NestWhile[If[EvenQ[#], #/2, 3#-1] &, n, FreeQ[{1, 5, 17}, #] &]; Select[Range[156], colln[#] == 1 &] (* Jayanta Basu, Jun 06 2013 *)

Crossrefs

Positive integers not in A037084.

Cf. A039501, A039502, A039503, A039504, A039505.

Sequence in context: A293635 A123586 A257121 * A160649 A341059 A190203

Adjacent sequences: A039497 A039498 A039499 * A039501 A039502 A039503

Keyword

nonn,easy

Author

Christian G. Bower, Feb 15 1999

Status

approved