A102246 Number of distinct prime factors of prime p concatenated p-1 times.

1, 2, 3, 5, 7, 9, 10, 10, 10, 11, 19, 16, 14, 20, 9, 12

Offset

1,2

Links

Table of n, a(n) for n=1..16.

Dario Alejandro Alpern, Factorization using the Elliptic Curve Method.

Example

If p=2, then the number of distinct prime factors of 2 is 1 since 2 is prime.
If p=3, then the number of distinct prime factors of 33 is 2.
If p=5, then the number of distinct prime factors of 5555 is 3.
If p=7, then the number of distinct prime factors of 777777 is 5.

Mathematica

f[n_] := Length[ FactorInteger[ FromDigits[ Flatten[ Table[ IntegerDigits[ Prime[n]], {Prime[n] - 1}]] ]]]; Table[ f[n], {n, 10}]
dpf[n_]:=Module[{p=Prime[n]}, PrimeNu[FromDigits[Flatten[ IntegerDigits/@ Table[p, {p-1}]]]]]; Array[dpf, 16] (* Harvey P. Dale, Aug 20 2013 *)

Crossrefs

Cf. A101081, A102245.

Sequence in context: A118784 A193889 A177922 * A089743 A080587 A342190

Adjacent sequences: A102243 A102244 A102245 * A102247 A102248 A102249

Keyword

nonn,base

Author

Parthasarathy Nambi, Feb 18 2005

Extensions

More terms from Robert G. Wilson v, Feb 21 2005

Corrected and extended by Harvey P. Dale, Aug 20 2013

Status

approved