A197952 Numbers n such that sigma(phi(n))/sigma(n) = 5.

1033474069, 1604277377, 2741806637, 9941342981, 14754456491, 14859359791, 15887724883, 16990353761, 17266051069, 20892536447, 21776951239, 24435763193, 25165559143, 32325726313, 38313868379, 38580669727, 38856433193, 47906215417, 49094416289, 56237053007

Offset: 1

Author

Donovan Johnson, Oct 19 2011

Keywords

• nonn

Examples

			sigma(phi(25165559143))/sigma(25165559143) = 127671828480/25534365696 = 5.
		

Crossrefs

Cf. A033631, A066831, A067382, A067383, A067384, A067385.

Programs

PARI

for(n=1033474069, 3*10^10, if(sigma(eulerphi(n))/sigma(n)==5, print1(n, ", ")))

Extensions

a(14)-a(20) from Donovan Johnson, Nov 11 2011