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

1, 2, 8, 32, 128, 864, 3456, 7776, 31104, 279936, 497664, 1990656, 4478976, 17915904, 62208000, 97200000, 559872000, 874800000, 1555200000, 6220800000, 13996800000, 55987200000

Offset

1,2

Comments

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

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, ...

Links

Table of n, a(n) for n=1..22.

Mathematica

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

Crossrefs

Cf. A072911, A181659, A331273.

Sequence in context: A081294 A004171 A009117 * A160637 A183895 A228921

Adjacent sequences: A331404 A331405 A331406 * A331408 A331409 A331410

Keyword

nonn,more

Author

Amiram Eldar, Feb 25 2020

Status

approved