A039504 -id:A039504 - cp's OEIS frontend

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

Christian G. Bower, Feb 15 1999

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

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

Positive integers not in A037084.

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

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

A039505 Odd numbers from A039502.

Original entry on oeis.org

17, 21, 23, 25, 31, 33, 37, 41, 45, 49, 55, 61, 67, 73, 83, 91, 99, 109, 111, 117, 123, 131, 147, 153, 163, 165, 175, 179, 185, 195, 197, 209, 213, 219, 221, 225, 229, 233, 239, 243, 247, 257, 261, 263, 267, 277, 279, 291, 293, 295, 305, 311, 313, 319, 321

Offset: 1

Christian G. Bower, Feb 15 1999

Cf. A037084, A039500-A039504.

colln[n_]:= NestWhile[If[EvenQ[#], #/2, 3#-1] &, n, FreeQ[{1, 5, 17}, #] &]; Select[Range[1, 321, 2], colln[#] == 17 &] (* Jayanta Basu, Jun 06 2013 *)

cp's OEIS Frontend

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

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