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%I #25 Apr 11 2020 10:29:36
%S 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,
%T 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,
%U 1,1,1,3,1,1,1,1,1,1,1,3,3,1,1,1,1,1,1
%N Sum of the iterated exponential totient function (A072911).
%C Analogous to A092693 with the exponential totient function ephi instead of the Euler totient function phi (A000010).
%C a(n) = 1 for n > 1 which is cubefree (A004709) and a(n) > 1 for n in A046099.
%H Amiram Eldar, <a href="/A331273/b331273.txt">Table of n, a(n) for n = 1..10000</a>
%e a(8) = ephi(8) + ephi(ephi(8)) = 2 + 1 = 3 (where ephi is A072911).
%t ephi[n_] := Times @@ EulerPhi[FactorInteger[n][[;; , 2]]]; s[n_] := Plus @@ FixedPointList[ephi, n] - n - 1; Array[s, 100]
%Y Cf. A004709, A046099, A072911, A092693.
%K nonn
%O 1,8
%A _Amiram Eldar_, Feb 25 2020