A078167 Numbers k such that phi(k) is a perfect 7th power.

1, 2, 255, 256, 272, 320, 340, 384, 408, 480, 510, 21845, 32768, 32896, 34816, 34952, 40960, 41120, 43520, 43690, 49152, 49344, 52224, 52428, 61440, 61680, 65280, 280999, 281587, 282637, 282949, 283897, 294409, 297449, 300409, 302039, 304399

Offset

1,2

Links

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

Example

phi of the sequence includes 1, 128, 16384, 279936, etc..; powers arise several times; a(3) = A053576(7) = 255; in sequence rather large jumps arise when power of new numbers appear.

Mathematica

k=7; Do[s=EulerPhi[n]^(1/k); If[IntegerQ[s], Print[n]], {n, 1, 1000000}]

Prog

(PARI) is(n)=ispower(eulerphi(n), 7) \\ Charles R Greathouse IV, Apr 24 2020

Crossrefs

Cf. A039770 (square), A039771 (cube), A078164 (4th), A078165 (5th), A078166 (6th), A078167 (7th, this sequence), A078168 (8th), A078169 (9th), A078170 (10th power), A001317, A053576, A045544, A000010.

Sequence in context: A370367 A070782 A370965 * A004875 A067480 A062077

Adjacent sequences: A078164 A078165 A078166 * A078168 A078169 A078170

Keyword

nonn

Author

Labos Elemer, Nov 27 2002

Status

approved