A138789 a(n) = number of distinct prime divisors of A104759(n).

0, 2, 2, 2, 3, 2, 2, 3, 3, 2, 2, 4, 4, 2, 5, 4, 2, 3, 7, 4, 4, 3, 3, 2, 5, 3, 5, 2, 3, 6, 6, 3, 3, 5, 5, 7, 3, 3, 4, 3, 3, 4, 4, 5, 3, 5, 7, 3, 5, 6, 6, 5, 4, 5, 2, 6, 4, 6, 4, 4, 7, 6, 5, 5, 6, 9, 5, 5, 7, 5, 5, 5, 5, 6, 6, 4, 4, 4, 5, 8, 7, 6, 4, 5, 4, 4, 9

Offset: 1

Author

Artur Jasinski, Mar 30 2008

Keywords

• nonn
• base

Links

• Sean A. Irvine, Table of n, a(n) for n = 1..165

Crossrefs

Cf. A001221, A104759, A000422, A116504, A007908, A116505.

Programs

Mathematica

lst = {}; Do[lst = Join[lst, IntegerDigits[n]], {n, 1, 50}]; Table[Length[FactorInteger[FromDigits[Reverse[lst[[Range[1,n]]]]]]], {n, 1, Length[lst]}] (* Robert Price, Mar 24 2015 *)

Formula

a(n) = A001221(A104759(n)). - Michel Marcus, Jun 30 2024

Extensions

Entire sequence corrected by Robert Price, Mar 24 2015

More terms from Sean A. Irvine, Jul 21 2024