A104658 Number of distinct prime factors of 23 concatenated n times.

1, 2, 5, 4, 4, 7, 4, 6, 8, 7, 6, 10, 6, 8, 13, 11, 6, 11, 3, 11, 14, 10, 6, 13, 10, 9, 12, 12, 8, 20, 5, 15, 14, 10, 12, 17, 7, 6, 15, 15

Offset

1,2

Links

Table of n, a(n) for n=1..40.

Formula

a(n) = A001221((23*100^n-23)/99). - R. J. Mathar, Aug 24 2011

Example

Number of distinct prime factors of 23 is 1 (prime).
Number of distinct prime factors of 2323 is 2.
Number of distinct prime factors of 232323 is 5.

Maple

A104658 := proc(n) local x ; x := 23 ; for j from 2 to n do x := 100*x+23 ; end do; numtheory[factorset](%) ; nops(%) ; end proc: # R. J. Mathar, Aug 24 2011

Mathematica

Table[PrimeNu[FromDigits[PadRight[{}, 2n, {2, 3}]]], {n, 40}] (* or *) PrimeNu[NestList[100#+23&, 23, 40]] (* Harvey P. Dale, May 21 2012 *)

Crossrefs

Cf. A001221.

Sequence in context: A021397 A325941 A374391 * A335566 A231730 A095758

Adjacent sequences: A104655 A104656 A104657 * A104659 A104660 A104661

Keyword

nonn

Author

Parthasarathy Nambi, Apr 21 2005

Status

approved