A331273 Sum of the iterated exponential totient function (A072911).

0, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 1, 1

Offset: 1

Author

Amiram Eldar, Feb 25 2020

Keywords

• nonn

Comments

Analogous to A092693 with the exponential totient function ephi instead of the Euler totient function phi (A000010).

a(n) = 1 for n > 1 which is cubefree (A004709) and a(n) > 1 for n in A046099.

Examples

			a(8) = ephi(8) + ephi(ephi(8)) = 2 + 1 = 3 (where ephi is A072911).
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004709, A046099, A072911, A092693.

Programs

Mathematica

ephi[n_] := Times @@ EulerPhi[FactorInteger[n][[;; , 2]]]; s[n_] := Plus @@ FixedPointList[ephi, n] - n - 1; Array[s, 100]