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A102621 Number of distinct prime factors of (nonprime A018252(n) concatenated A018252(n) times). 1
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 (list; graph; refs; listen; history; text; internal format)
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: A011223 A188670 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

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Last modified October 21 19:16 EDT 2021. Contains 348155 sequences. (Running on oeis4.)