A211413 Numbers m such that phi(m) is a power of the product of the distinct prime factors of m.

1, 4, 8, 16, 18, 32, 64, 108, 128, 250, 256, 512, 648, 1024, 2048, 2500, 3888, 4096, 6174, 8192, 16384, 23328, 25000, 32768, 41154, 65536, 101250, 131072, 139968, 250000, 259308, 262144, 524288, 839808, 1048576, 1542294, 2097152, 2500000, 2839714

Offset: 1

Author

Giovanni Resta, Feb 10 2013

Keywords

• nonn

Comments

Sequence contains the numbers 2^(k+1), 2^k*3^(k+1) and 25*10^k, for k > 0.

a(226) > 10^18.

Examples

			m = 178726991395974 = 2*3*7^2*883^4 and phi(m) = 2^3*3^3*7^3*883^3.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..225

Crossrefs

Cf. A105261.

Subsequence of A055744.

Programs

Mathematica

Select[Range[10^5], # == 1 || IntegerQ @ Log[Times @@ First /@ FactorInteger @ #, EulerPhi @ #] &]