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

Author

Giovanni Resta, Jan 31 2006

Keywords

• nonn

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

Examples

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

Crossrefs

Cf. A000010, A000203.

Programs

PARI

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

Extensions

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

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