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 A331407 Numbers at which the sum of the iterated exponential totient function (A331273) attains a record. 2

%I

%S 1,2,8,32,128,864,3456,7776,31104,279936,497664,1990656,4478976,

%T 17915904,62208000,97200000,559872000,874800000,1555200000,6220800000,

%U 13996800000,55987200000

%N Numbers at which the sum of the iterated exponential totient function (A331273) attains a record.

%C Analogous to A181659 with the exponential totient function (A072911) instead of the Euler totient function phi (A000010).

%C The corresponding record values are 0, 1, 3, 5, 7, 11, 13, 19, 27, 37, 43, 51, 61, 75, 83, 101, 123, 147, 165, 195, 243, 293, ...

%t ephi[n_] := Times @@ EulerPhi[FactorInteger[n][[;; , 2]]]; s[n_] := Plus @@ FixedPointList[ephi, n] - n - 1; seq = {}; smax = -1; Do[s1 = s[n]; If[s1 > smax, smax = s1; AppendTo[seq, n]], {n, 1, 5000}]; seq

%Y Cf. A072911, A181659, A331273.

%K nonn,more

%O 1,2

%A _Amiram Eldar_, Feb 25 2020

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Last modified September 25 06:05 EDT 2020. Contains 337335 sequences. (Running on oeis4.)