A039502 Iterations of "n->n/2 if n even, n->3n-1 if n odd" (A001281) starting at these numbers reach 17.

17, 21, 23, 25, 31, 33, 34, 37, 41, 42, 45, 46, 49, 50, 55, 61, 62, 66, 67, 68, 73, 74, 82, 83, 84, 90, 91, 92, 98, 99, 100, 109, 110, 111, 117, 122, 123, 124, 131, 132, 134, 136, 146, 147, 148, 153, 163, 164, 165, 166, 168, 175, 179, 180, 182, 184, 185, 195, 196

Offset: 1

Author

Christian G. Bower, Feb 15 1999

Keywords

• nonn
• easy

Crossrefs

Cf. A037084, A039500-A039505.

Programs

Mathematica

colln[n_]:= NestWhile[If[EvenQ[#], #/2, 3#-1] &, n, FreeQ[{1, 5, 17}, #] &]; Select[Range[196], colln[#] == 17 &] (* Jayanta Basu, Jun 06 2013 *)