login
Number of prime divisors (counted without multiplicity) of A138613(n).
2

%I #16 Dec 12 2019 03:27:29

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

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

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

%t PrimeNu[NestList[DivisorSigma[2,#]&,2,12]] (* _Harvey P. Dale_, Aug 19 2017 *)

%Y Cf. A138613, A079488, A001221.

%K nonn,more

%O 1,3

%A _N. J. A. Sloane_, Sep 20 2008

%E a(10)-a(12) from _Donovan Johnson_, Nov 17 2008

%E a(13)-a(16) from _Daniel Suteu_, Dec 11 2019