A104660 Number of distinct prime divisors of 44...443 (with n 4s).

1, 1, 2, 2, 1, 3, 3, 1, 2, 2, 1, 2, 2, 3, 3, 3, 3, 3, 4, 3, 3, 6, 3, 4, 3, 3, 6, 4, 1, 5, 1, 4, 3, 5, 3, 6, 4, 2, 6, 2, 2, 3, 5, 3, 4, 4, 4, 2, 2, 4, 4, 3, 4, 5, 6, 3, 3, 5, 2, 4, 3, 5, 4, 4, 3, 6, 4, 3, 6, 6, 4, 5, 4, 2, 4, 5, 2, 4, 5, 6, 4, 4, 3, 6, 5, 4, 5

Offset: 1

Author

Parthasarathy Nambi, Apr 21 2005

Keywords

• nonn
• base

Examples

			The number of distinct prime divisors of 43 is 1 (prime).
The number of distinct prime divisors of 443 is 1 (prime).
The number of distinct prime divisors of 4443 is 2.
		

Links

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

Crossrefs

Cf. A001221, A104518, A173770.

Programs

Maple

A104660 := proc(n) x := [3,seq(4,k=1..n)] ; add(op(i,x)*10^(i-1),i=1..nops(x)) ; numtheory[factorset](%) ; nops(%) ; end proc:
seq(A104660(n),n=1..45) ; # R. J. Mathar, Aug 23 2011

Mathematica

Table[PrimeNu[FromDigits[Join[Table[4, {n}], {3}]]], {n, 50}] (* Alonso del Arte, Aug 23 2011 *)
Table[PrimeNu[FromDigits[PadLeft[{3},n,4]]],{n,2,70}] (* Harvey P. Dale, Aug 22 2016 *)

Formula

a(n) = A001221(A173770(n+1)). - Amiram Eldar, Jan 25 2020

Extensions

More terms from R. J. Mathar and Alonso del Arte, Aug 23 2011

More terms from Amiram Eldar, Jan 25 2020