A104543 Number of distinct prime divisors of 55...559 (with n 5s).

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

Offset: 1

Author

Parthasarathy Nambi, Apr 20 2005

Keywords

• nonn
• base

Examples

			The number of distinct prime divisors of 59 is 1 (prime).
The number of distinct prime divisors of 559 is 2.
The number of distinct prime divisors of 5559 is 3.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..202

Crossrefs

Cf. A104484, A104483.

Programs

Maple

A104543 := proc(n) local x ;x := [9,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 + 31)/9], {n,0,50}] (* G. C. Greubel, May 10 2017 *)
Table[PrimeNu[FromDigits[PadLeft[{9},n,5]]],{n,2,90}] (* Harvey P. Dale, Apr 22 2020 *)

Formula

a(n) = A001221((31+50*10^n)/9). - R. J. Mathar, Aug 24 2011

Extensions

More terms from Amiram Eldar, Jan 25 2020