A105255 Number of distinct prime divisors of 88...889 (with n 8's).

1, 1, 2, 2, 2, 2, 2, 2, 5, 3, 2, 5, 3, 1, 6, 4, 1, 4, 4, 3, 4, 4, 2, 3, 3, 3, 4, 4, 2, 6, 5, 4, 6, 3, 1, 5, 6, 2, 6, 4, 3, 7, 5, 2, 8, 7, 4, 7, 5, 4, 7, 3, 7, 5, 3, 3, 9, 6, 5, 3, 3, 3, 7, 3, 4, 6, 4, 2, 6, 7, 5, 7, 7, 4, 7, 6, 4, 5, 3, 4, 6, 2, 2, 7, 5, 3, 9, 6, 4, 8, 6, 7, 5, 2, 5, 6, 5, 5, 7, 7

Offset

0,3

Links

Amiram Eldar, Table of n, a(n) for n = 0..225

Formula

a(n) = A001221(A059482(n+1)). - Michel Marcus, Jan 27 2014

Example

The number of distinct prime divisors of 89 is 1 (prime).
The number of distinct prime divisors of 889 is 2.
The number of distinct prime divisors of 8889 is 2.

Mathematica

Table[PrimeNu[(8*10^(n + 1) + 1)/9], {n, 0, 50}] (* G. C. Greubel, May 16 2017 *)

Prog

(PARI) a(n) = omega((8*10^(n+1)+1)/9); \\ Michel Marcus, Jan 27 2014

Crossrefs

Cf. A104543.

Sequence in context: A244461 A366811 A343925 * A351023 A140818 A139813

Adjacent sequences: A105252 A105253 A105254 * A105256 A105257 A105258

Keyword

nonn,base

Author

Parthasarathy Nambi, Apr 29 2005

Status

approved