A003124 One of the basic cycles in the x->3x-1 (x odd) or x/2 (x even) problem.

17, 50, 25, 74, 37, 110, 55, 164, 82, 41, 122, 61, 182, 91, 272, 136, 68, 34, 17, 50, 25, 74, 37, 110, 55, 164, 82, 41, 122, 61, 182, 91, 272, 136, 68, 34, 17, 50, 25, 74, 37, 110, 55, 164, 82, 41, 122, 61, 182, 91, 272, 136, 68, 34

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Examples

			17 is odd, so the next term is 3 * 17 - 1 = 50.
50 is even, so the next term is 50/2 = 25.
		

References

• Richard K. Guy, Unsolved Problems in Number Theory, E16.
• H.-O. Peitgen et al., Chaos and Fractals, Springer, p. 33.

Programs

Mathematica

Abs[NestList[If[EvenQ[#], #/2, 3# + 1]&, -17, 100]] (* Alonso del Arte, May 19 2015 *)

PARI

a=34;A003124=vector(100,i,a=if(bittest(a,0),3*a-1,a/2)) \\ M. F. Hasler, Aug 29 2015

PARI

A003124(n,a=17)={for(i=1,n%17,a=if(bittest(a,0),3*a-1,a\2));a} \\ M. F. Hasler, Aug 29 2015