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

Author

Labos Elemer, Dec 04 2001

Keywords

• nonn

Links

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

Crossrefs

Cf. A001159, A001221.

Programs

Mathematica

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

PARI

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

Formula

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