A074891 Numbers n such that sigma(n) = phi(3n).

15, 35, 357, 1045, 3339, 5049, 10659, 12441, 24871, 24969, 29029, 50065, 58435, 64285, 87685, 99693, 132957, 137885, 140335, 353133, 423657, 596037, 655707, 734517, 745503, 894387, 1390753, 1406427, 1529983, 1641783, 1739507, 1823877

Offset: 1

Author

Joseph L. Pe, Sep 13 2002

Keywords

• nonn

Examples

			sigma(15) = 24 = phi(3 * 15), so 15 is a term of the sequence.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..500

Programs

Mathematica

Select[ Range[1936556], EulerPhi[3# ] == DivisorSigma[1, # ] &]

PARI

is(n)=sigma(n)==eulerphi(3*n) \\ Charles R Greathouse IV, Dec 09 2013

Extensions

Edited and extended by Robert G. Wilson v, Sep 17 2002