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A078169
Numbers k such that phi(k) is a perfect 9th power.
8
1, 2, 771, 1024, 1028, 1088, 1280, 1360, 1536, 1542, 1632, 1920, 2040, 327685, 524288, 524296, 526336, 557056, 559232, 655360, 655370, 657920, 696320, 699040, 786432, 786444, 789504, 835584, 838848, 983040, 986880, 1044480, 1048560
OFFSET
1,2
LINKS
EXAMPLE
phi of the sequence includes 1, 512, 262144,.. etc.; powers arise several times; a(3) = A053576(9) = 771; in sequence smoother ranges and quite large jumps arise when power of new numbers appear as phi-values.
MATHEMATICA
k=9; Do[s=EulerPhi[n]^(1/k); If[IntegerQ[s], Print[n]], {n, 1, 10000000}]
PROG
(PARI) is(n)=ispower(eulerphi(n), 9) \\ Charles R Greathouse IV, Apr 24 2020
CROSSREFS
Cf. A039770 (square), A039771 (cube), A078164 (4th), A078165 (5th), A078166 (6th), A078167 (7th), A078168 (8th), A078169 (9th, this sequence), A078170 (10th power), A001317, A053576, A045544, A000010.
Sequence in context: A344663 A167448 A320481 * A226779 A375844 A243409
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 27 2002
STATUS
approved