A259103 Number of steps to get from n to 1 by process of replacing with the Euler totient function phi if the result is odd, or dividing by 2 if even.

0, 1, 2, 2, 3, 3, 4, 3, 4, 4, 5, 4, 5, 5, 4, 4, 5, 5, 6, 5, 5, 6, 7, 5, 6, 6, 6, 6, 7, 5, 6, 5, 6, 6, 6, 6, 7, 7, 6, 6, 7, 6, 7, 7, 6, 8, 9, 6, 7, 7, 6, 7, 8, 7, 7, 7, 7, 8, 9, 6, 7, 7, 7, 6, 7, 7, 8, 7, 8, 7, 8, 7, 8, 8, 7, 8, 7, 7, 8, 7, 8, 8, 9, 7, 7, 8, 8

Offset

1,3

Links

Table of n, a(n) for n=1..87.

Example

a(7)= 4 because 7 -> phi(7)= 6 -> 3 -> phi(3)= 2 -> 1, hence the trajectory {7 -> 6 -> 3 -> 2 -> 1} with 4 iterations.

Mathematica

f[n_]:=Module[{a=n, k=0}, While[a!=1, k++; If[EvenQ[a], a=a/2, a=EulerPhi[a]]]; k]; Table[f[n], {n, 1, 150}]

Crossrefs

Cf. A000010.

Sequence in context: A139141 A122953 A259847 * A334200 A128998 A137813

Adjacent sequences: A259100 A259101 A259102 * A259104 A259105 A259106

Keyword

nonn,easy

Author

Michel Lagneau, Jul 07 2015

Status

approved