A102745 Number of distinct prime factors of four consecutively concatenated primes.

1, 3, 4, 3, 4, 3, 3, 2, 3, 2, 3, 3, 3, 4, 4, 3, 3, 4, 1, 2, 4, 3, 1, 3, 4, 3, 4, 4, 3, 2, 5, 2, 3, 1, 1, 2, 2, 2, 2, 2, 3, 5, 3, 2, 4, 4, 2, 3, 5, 4, 3, 4, 3, 5, 3, 3, 3, 2, 4, 2, 4, 3, 3, 3, 4, 4, 2, 3, 2, 3, 2, 3, 2, 4, 3, 1, 2, 4, 3, 3, 3, 4, 4, 2, 4, 3, 4, 5, 4, 4, 2, 4, 5, 4, 3, 1, 3, 3, 4, 3, 4, 1, 2, 3, 4

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

2357 is a prime, thus the number of distinct prime factors is 1.
The number of distinct prime factors of 31374143 is 3.
67717379 is prime, thus the number of distinct prime factors is 1.

Mathematica

f[n_] := Length[ FactorInteger[ FromDigits[ Flatten[ Table[ IntegerDigits[ Prime[i]], {i, n, n + 3}]] ]]]; Table[ f[n], {n, 105}] (* Robert G. Wilson v, Feb 22 2005 *)
PrimeNu[FromDigits[Flatten[IntegerDigits/@#]]]&/@Partition[ Prime[ Range[ 120]], 4, 1] (* Harvey P. Dale, Mar 07 2020 *)

Crossrefs

Sequence in context: A293072 A120447 A083021 * A108026 A010702 A345439

Adjacent sequences: A102742 A102743 A102744 * A102746 A102747 A102748

Keyword

nonn,base

Author

Parthasarathy Nambi, Feb 08 2005

Extensions

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

Status

approved