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A102746
Number of distinct prime factors of concatenation of first n primes.
0
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
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
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Feb 08 2005
EXTENSIONS
More terms from Robert G. Wilson v, Feb 22 2005
STATUS
approved