A101081 Number of distinct prime factors of (prime p concatenated p times).

2, 2, 3, 3, 6, 6, 6, 3, 6, 8, 5, 7, 7, 8, 6, 6, 6, 10, 5, 5, 7, 10, 10, 9, 7, 7, 8, 11, 9, 8, 9, 14, 8

Offset

1,1

Links

Table of n, a(n) for n=1..33.

Dario Alejandro Alpern, Factorization using the Elliptic Curve Method.

Example

The number of distinct prime factors of 22 is 2.
The number of distinct prime factors of 333 is 2.
The number of distinct prime factors of 55555 is 3.
Then the number of distinct prime factors of 7777777 is 3.
a(16) comes from 53 * 107 * 1659431 * 1325815267337711173 * 47198858799491425660200071 * 9090909090909090909090909090909090909090909090909091. a(17) comes from 59 * 1889 * 2559647034361 * 1090805842068098677837 * 4411922770996074109644535362851087 * 4340876285657460212144534289928559826755746751. a(18) comes from 61 * 733 * 4637 * 81131 * 329401 * 974293 * 1360682471 * 106007173861643 * 7061709990156159479 * 11205222530116836855321528257890437575145023592596037161. Concerning a(19) = 67*(100^67-1)/99 = 67 * 493121 * 79863595778924342083 * 25648528130160606364784685146362888405160909090909090909090909090911655761903925151545569377605545379749607 (C107). - Robert G. Wilson v, Jan 27 2005

Mathematica

f[n_] := Length[ FactorInteger[ FromDigits[ Flatten[ Table[ IntegerDigits[ Prime[n]], {Prime[n]}] ]]]]; Table[ f[n], {n, 15}] (* Robert G. Wilson v, Jan 27 2005 *)
Table[PrimeNu[FromDigits[Flatten[IntegerDigits/@PadRight[{}, p, p]]]], {p, Prime[Range[33]]}] (* Harvey P. Dale, Apr 06 2023 *)

Crossrefs

Cf. A101459.

Sequence in context: A145787 A096111 A358337 * A147795 A258186 A357415

Adjacent sequences: A101078 A101079 A101080 * A101082 A101083 A101084

Keyword

nonn,base,more

Author

Parthasarathy Nambi, Jan 21 2005

Extensions

a(11)-a(15) from Ray Chandler, Jan 25 2005

a(16)-a(18) from Robert G. Wilson v, Jan 27 2005

Corrected and extended to a(33) by D. S. McNeil, Jan 07 2011

Status

approved