A102621 Number of distinct prime factors of (nonprime A018252(n) concatenated A018252(n) times).

0, 3, 6, 5, 3, 8, 10, 9, 13, 11, 11, 12, 13, 11, 13, 10, 10, 11, 13, 21, 15, 14, 11, 13, 17, 7, 14, 16

Offset

1,2

Links

Table of n, a(n) for n=1..28.

Dario A. Alpern, Factorization using the Elliptic curve method.

Formula

a(n) = A001221(A102622(n)). - R. J. Mathar, Aug 24 2011

Example

For n=2, the number of distinct prime factors of 4444 is 3.
For n=3, the number of distinct prime factors of 666666 is 6.
For n=4, the number of distinct prime factors of 88888888 is 5.
For n=5, the number of distinct prime factors of 999999999 is 3.

Maple

read("transforms") ;
A102621 := proc(n) c := A018252(n) ; x := c ; for j from 2 to c do x := digcat2(x, c) ; end do; A001221(x) ; end proc: # R. J. Mathar, Aug 24 2011

Mathematica

PrimeNu/@(FromDigits/@(Flatten[Table[IntegerDigits[#], #]]&/@Select[ Range[ 40], !PrimeQ[#]&])) (* Harvey P. Dale, Sep 03 2018 *)

Crossrefs

Cf. A101081.

Sequence in context: A188670 A361985 A346602 * A289504 A347538 A159066

Adjacent sequences: A102618 A102619 A102620 * A102622 A102623 A102624

Keyword

nonn,base,less

Author

Parthasarathy Nambi, Jan 31 2005

Extensions

More terms from Harvey P. Dale, Sep 03 2018

Status

approved