A113939 Numbers k such that sigma(k) and phi(k) are both perfect cubes.

1, 300118, 2250885, 5294800, 76336260, 141483384, 242375035, 453280968, 456345036, 461356896, 478240392, 537375930, 1139523375, 1180718238, 1227111595, 1599634410, 5043835125, 5229921340, 5610392513, 6087775939, 6376494509, 11038341720, 11044670824

Offset

1,2

Comments

phi(k) = A000010(k) is the Euler totient function, while sigma(k) = A000203(k) is the sum of divisors of k.

Intersection of A020477 and A039771. - Michel Marcus, Jan 04 2014

Links

Table of n, a(n) for n=1..23.

Example

sigma(2250885) = 168^3 and phi(2250885) = 96^3.

Prog

(PARI) for(n=1, 10^9, if(ispower(eulerphi(n), 3), if(ispower(sigma(n), 3), print1(n ", ")))) \\ Donovan Johnson, Jan 04 2014

Crossrefs

Cf. A000010, A000203.

Sequence in context: A227700 A050257 A283209 * A023686 A250506 A156998

Adjacent sequences: A113936 A113937 A113938 * A113940 A113941 A113942

Keyword

nonn

Author

Giovanni Resta, Jan 31 2006

Extensions

a(7)-a(20) from Donovan Johnson, Feb 06 2010

a(21)-a(23) from Donovan Johnson, Jan 04 2014

Status

approved