login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A331407 Numbers at which the sum of the iterated exponential totient function (A331273) attains a record. 2
1, 2, 8, 32, 128, 864, 3456, 7776, 31104, 279936, 497664, 1990656, 4478976, 17915904, 62208000, 97200000, 559872000, 874800000, 1555200000, 6220800000, 13996800000, 55987200000 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 14 07:59 EDT 2020. Contains 336477 sequences. (Running on oeis4.)