A033766 Number of prime divisors (counted without multiplicity) of A138613(n).

1, 1, 2, 3, 6, 8, 11, 20, 29, 47, 78, 129, 230, 400, 710, 1221

Offset

1,3

Comments

The old entry with this sequence number was a duplicate of A035162.

Links

Table of n, a(n) for n=1..16.

Mathematica

PrimeNu[NestList[DivisorSigma[2, #]&, 2, 12]] (* Harvey P. Dale, Aug 19 2017 *)

Crossrefs

Cf. A138613, A079488, A001221.

Sequence in context: A353903 A325547 A242340 * A129340 A276588 A275951

Adjacent sequences: A033763 A033764 A033765 * A033767 A033768 A033769

Keyword

nonn,more

Author

N. J. A. Sloane, Sep 20 2008

Extensions

a(10)-a(12) from Donovan Johnson, Nov 17 2008

a(13)-a(16) from Daniel Suteu, Dec 11 2019

Status

approved