A104518 Number of distinct prime divisors of 55...3 (with n 5s).

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

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..199

Formula

a(n) = A001221(A173802(n+1)). - R. J. Mathar, Aug 24 2011

Example

The number of distinct prime divisors of 53 is 1 (prime) which is the first term in the sequence.
The number of distinct prime divisors of 553 is 2 which is the second term in the sequence.
The number of distinct prime divisors of 5553 is 2 which is the third term in the sequence.

Maple

A104518 := proc(n) local x ; x := [3, seq(5, k=1..n)] ; add(op(i, x)*10^(i-1), i=1..nops(x)) ; numtheory[factorset](%) ; nops(%) ; end proc: # R. J. Mathar, Aug 24 2011

Mathematica

Table[PrimeNu[(50*10^n - 23)/9], {n, 0, 50}] (* G. C. Greubel, May 06 2017 *)

Crossrefs

Cf. A001221, A173802.

Sequence in context: A271778 A326702 A133563 * A329030 A027388 A114295

Adjacent sequences: A104515 A104516 A104517 * A104519 A104520 A104521

Keyword

nonn,base

Author

Parthasarathy Nambi, Apr 19 2005

Extensions

More terms from Amiram Eldar, Jan 25 2020

Status

approved