A105973 Number of distinct prime divisors of 88...883 (with n 8's).

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

Offset

0,4

Links

Amiram Eldar, Table of n, a(n) for n = 0..201

Formula

a(n) = A001221(A173811(n+1)). - Michel Marcus, Jan 27 2014

Example

The number of distinct prime divisors of 83 is 1 (prime).
The number of distinct prime divisors of 883 is 1 (prime).
The number of distinct prime divisors of 8883 is 3.

Mathematica

Table[PrimeNu[FromDigits[PadLeft[{3}, n, 8]]], {n, 100}] (* Harvey P. Dale, Mar 08 2015 *)

Prog

(PARI) a(n) = omega((8*10^(n+1)-53)/9); \\ Michel Marcus, Jan 27 2014

Crossrefs

Cf. A104660, A104518, A104660.

Sequence in context: A236452 A056529 A087282 * A088429 A134658 A296518

Adjacent sequences: A105970 A105971 A105972 * A105974 A105975 A105976

Keyword

nonn,base

Author

Parthasarathy Nambi, Apr 28 2005

Status

approved