A061366 Numbers k such that phi(k)+sigma(k) is a perfect cube.

99, 814, 1371, 2047, 2883, 5816, 6105, 6851, 10718, 16744, 19390, 19651, 20080, 20115, 20820, 22015, 22165, 22550, 23035, 25976, 30090, 31999, 32130, 34479, 36492, 36865, 37043, 39942, 40347, 42591, 44475, 48667, 52377, 54213, 54321

Offset

1,1

Links

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

Example

phi(99)+sigma(99) = 60+156 = 216 = 6^3, so 99 is a term of the sequence.

Mathematica

Select[Range[10^5], IntegerQ[(EulerPhi[ # ] + DivisorSigma[1, # ])^(1/3)] &]

Prog

(PARI) isok(n) = ispower(eulerphi(n)+sigma(n), 3); \\ Michel Marcus, Sep 28 2019

Crossrefs

Cf. A000578, A065387.

Sequence in context: A321636 A154359 A185499 * A177686 A135219 A182672

Adjacent sequences: A061363 A061364 A061365 * A061367 A061368 A061369

Keyword

nonn,changed

Author

Joseph L. Pe, Feb 13 2002

Status

approved