A075868 tau(n) = phi(sum of prime factors of n).

3, 6, 15, 20, 21, 28, 35, 50, 66, 98, 99, 104, 105, 114, 125, 130, 154, 170, 210, 230, 276, 325, 351, 352, 363, 372, 374, 380, 414, 444, 459, 476, 532, 539, 558, 572, 580, 585, 608, 666, 693, 696, 845, 847, 950, 968, 975

Offset

2,1

Links

Table of n, a(n) for n=2..48.

Example

tau(50) = number of divisors of 50 = 6; phi(sum of prime factors of 50) = phi(2 + 5) = 6. Hence 50 is a term of the sequence.

Mathematica

Select[Range[2, 10^3], EulerPhi[Apply[Plus, Transpose[FactorInteger[ # ]][[1]]]] == DivisorSigma[0, # ] &]

Crossrefs

Sequence in context: A265486 A060304 A342555 * A162335 A289296 A310126

Adjacent sequences: A075865 A075866 A075867 * A075869 A075870 A075871

Keyword

nonn

Author

Joseph L. Pe, Oct 15 2002

Status

approved