A070807 Composite numbers n such that Cototient(totient(n))=A070556(n) is power of 2.

4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 24, 26, 28, 30, 32, 34, 35, 36, 39, 40, 42, 45, 48, 51, 52, 56, 58, 60, 64, 65, 68, 70, 72, 78, 80, 84, 85, 87, 90, 96, 102, 104, 105, 112, 116, 119, 120, 128, 130, 136, 140, 144, 145, 153, 156, 160, 168, 170, 174, 180, 192

Offset: 1

Author

Labos Elemer, May 08 2002

Keywords

• nonn

Examples

			n=87=3.29:phi[87]=56,56-phi[56]=56-24=32
		

Crossrefs

Cf. A070556, A051953, A054571, A070806, A070809-A070811.

Programs

Mathematica

Do[s= EulerPhi[n]-EulerPhi[EulerPhi[n]]; If[IntegerQ[Log[2, s]]&&!PrimeQ[n], Print[n]], {n, 1, 10000000}]