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

Author

N. J. A. Sloane, Sep 20 2008

Keywords

• nonn
• more

Comments

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

Crossrefs

Cf. A138613, A079488, A001221.

Programs

Mathematica

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

Extensions

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

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