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

1,2

Comments

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

a(226) > 10^18.

Links

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

Example

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

Mathematica

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

Crossrefs

Cf. A105261.

Subsequence of A055744.

Sequence in context: A055744 A141718 A195382 * A181310 A212110 A033310

Adjacent sequences: A211410 A211411 A211412 * A211414 A211415 A211416

Keyword

nonn

Author

Giovanni Resta, Feb 10 2013

Status

approved