2,1

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.

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

Sequence in context: A124518 A160724 A060304 this_sequence A162335 A095869 A069559

Adjacent sequences: A075865 A075866 A075867 this_sequence A075869 A075870 A075871

nonn

Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Oct 15 2002