A062385 Numbers k such that sigma(k) - phi(k) is a cube.

1, 30, 44, 87, 169, 247, 515, 630, 707, 910, 1067, 1255, 1356, 1691, 2128, 2188, 2291, 2438, 2574, 2627, 2747, 2867, 3668, 3689, 4063, 4295, 5206, 5359, 5999, 6331, 6583, 6835, 7719, 8286, 8968, 8991, 9383

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Example

sigma(30) - phi(30) = 72 - 8 = 64 = 4^3, so 30 is a term of the sequence.

Mathematica

Select[Range[10^4], IntegerQ[(DivisorSigma[1, # ] - EulerPhi[ # ])^(1/3)] &]

Prog

(PARI) select(k->ispower(sigma(k)-eulerphi(k), 3), [1..10000]) \\ Harry J. Smith, Aug 06 2009

Crossrefs

Sequence in context: A226727 A102843 A242445 * A164803 A152569 A381020

Adjacent sequences: A062382 A062383 A062384 * A062386 A062387 A062388

Keyword

nonn

Author

Joseph L. Pe, Feb 13 2002

Status

approved