A066102 Number of distinct prime factors of sigma_4(n), the sum of the 4th powers of divisors of n.

0, 1, 2, 3, 2, 3, 2, 2, 3, 3, 2, 5, 2, 3, 3, 4, 2, 4, 3, 5, 3, 3, 2, 4, 4, 3, 4, 5, 2, 4, 3, 5, 3, 3, 3, 4, 3, 3, 3, 4, 3, 4, 4, 5, 5, 3, 3, 5, 5, 5, 3, 5, 3, 4, 3, 4, 4, 3, 4, 6, 2, 4, 5, 4, 3, 4, 3, 5, 3, 4, 2, 5, 2, 4, 6, 6, 3, 4, 4, 6, 4, 4, 4, 6, 3, 4, 3, 4, 3, 6, 3, 5, 4, 4, 4, 7, 3, 6, 5, 5, 3, 4, 2, 4, 4

Offset

1,3

Links

Harry J. Smith, Table of n, a(n) for n=1..1000

Formula

a(n) = omega(sigma_4(n)) = A001221(A001159(n)).

Mathematica

Table[PrimeNu[DivisorSigma[4, n]], {n, 1, 50}] (* G. C. Greubel, May 08 2017 *)

Prog

(PARI) a(n) = { omega(sigma(n, 4)) } \\ Harry J. Smith, Nov 14 2009

Crossrefs

Cf. A001159, A001221.

Sequence in context: A276862 A371442 A175066 * A036048 A145384 A339601

Adjacent sequences: A066099 A066100 A066101 * A066103 A066104 A066105

Keyword

nonn

Author

Labos Elemer, Dec 04 2001

Status

approved