A078769 Numbers k such that k * phi(k)^2 < sigma(k)^2.

2, 3, 4, 6, 8, 10, 12, 14, 18, 20, 24, 30, 36, 42, 48, 60, 84, 90, 120

Offset: 0

Author

Jon Perry, Jan 09 2003

Keywords

• nonn

Examples

			8*phi(8)^2=128, sigma(8)^2=225 and 128 < 225, hence 8 is a term of the sequence.
		

Crossrefs

Cf. A064375.

Programs

PARI

for (n=1,1000, if (eulerphi(n)^2*n
				

Extensions

Name clarified by Sean A. Irvine, Jul 15 2025