A102746 Number of distinct prime factors of concatenation of first n primes.

1, 1, 2, 1, 3, 3, 2, 3, 3, 3, 5, 4, 3, 4, 3, 4, 4, 4, 2, 2, 3, 4, 3, 4, 4, 5, 2, 5, 3, 6, 5, 5, 7, 7, 7, 4, 4, 6, 4, 9

Offset

1,3

Links

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

Dario Alejandro Alpern, Factorization using the Elliptic Curve Method.

Hisanori Mishima, Smarandache consecutive prime sequences (n = 1 to 100).

Example

The number of distinct prime factors of 2 is 1 since it is a prime.
The number of distinct prime factors of 23 is 1 since it is a prime.
The number of distinct prime factors of 235 is 2.
The number of distinct prime factors of 2357 is 1 since it is a prime.

Mathematica

f[n_] := Length[ FactorInteger[ FromDigits[ Flatten[ Table[ IntegerDigits[ Prime[i]], {i, n}]] ]]]; Table[ f[n], {n, 15}] (* Robert G. Wilson v, Feb 22 2005 *)

Crossrefs

Sequence in context: A351599 A350743 A234200 * A287618 A123143 A128133

Adjacent sequences: A102743 A102744 A102745 * A102747 A102748 A102749

Keyword

nonn,base

Author

Parthasarathy Nambi, Feb 08 2005

Extensions

More terms from Robert G. Wilson v, Feb 22 2005

Status

approved