A058062 Number of distinct prime factors of sigma(n), the sum of the divisors of n.

0, 1, 1, 1, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 3, 1, 2, 2, 3, 1, 3, 2, 2, 3, 2, 1, 2, 2, 2, 2, 2, 2, 3, 2, 3, 3, 2, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 3, 3, 3, 2, 2, 2, 1, 3, 2, 2, 3, 2, 2, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 1, 3, 3, 2, 2, 3, 3, 3, 3, 3, 2, 3, 1, 2, 3, 3, 2, 2, 3, 2, 3, 2, 2, 4, 2

Offset

1,5

Links

G. C. Greubel, Table of n, a(n) for n = 1..5001

Formula

a(n) = A001221(A000203(n)).

Example

n=81, sigma(81) = 81+27+9+3+1 = 121 = 11^2, so a(81) = 1.

Mathematica

Table[PrimeNu[DivisorSigma[1, n]], {n, 50}] (* G. C. Greubel, May 20 2017 *)

Prog

(PARI) for(n=1, 50, print1(omega(sigma(n)), ", ")) \\ G. C. Greubel, May 20 2017

Crossrefs

Cf. A001221, A000203.

Sequence in context: A091267 A003643 A092788 * A102820 A355717 A024317

Adjacent sequences: A058059 A058060 A058061 * A058063 A058064 A058065

Keyword

nonn

Author

Labos Elemer, Nov 23 2000

Extensions

Offset corrected by Sean A. Irvine, Jul 22 2022

Status

approved