A363680 - OEIS

A363680

Number of iterations of phi(x) at n needed to reach a cube.

0, 1, 2, 2, 3, 2, 3, 0, 3, 3, 4, 3, 4, 3, 1, 1, 2, 3, 4, 1, 4, 4, 5, 1, 2, 4, 0, 4, 5, 1, 2, 2, 2, 2, 2, 4, 5, 4, 2, 2, 3, 4, 5, 2, 2, 5, 6, 2, 5, 2, 3, 2, 3, 4, 3, 2, 5, 5, 6, 2, 3, 2, 5, 0, 3, 2, 3, 3, 3, 2, 3, 2, 3, 5, 3, 5, 3, 2, 3, 3, 5, 3, 4, 2, 1, 5, 3

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OFFSET

1,3

LINKS

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

MATHEMATICA

a[n_] := a[n] = If[IntegerQ[Surd[n, 3]], 0, a[EulerPhi[n]] + 1]; Array[a, 100] (* Amiram Eldar, Jun 14 2023 *)

PROG

(Python)

from sympy import totient, integer_nthroot

def a(n):

x = n