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 A078167 Numbers k such that phi(k) is a perfect 7th power. 8
 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 (list; graph; refs; listen; history; text; internal format)
 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: A304211 A224828 A070782 * A004875 A067480 A062077 Adjacent sequences: A078164 A078165 A078166 * A078168 A078169 A078170 KEYWORD nonn AUTHOR Labos Elemer, Nov 27 2002 STATUS approved

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Last modified October 3 09:41 EDT 2023. Contains 365854 sequences. (Running on oeis4.)