A103178 Number of divisors of the decimal concatenation of the first n primes.

2, 2, 4, 2, 8, 8, 4, 8, 8, 8, 32, 24, 8, 16, 8, 16, 16, 16, 4, 8, 8, 16, 8, 24, 16, 64, 4, 32, 8, 128, 32, 32, 128, 128, 192, 16, 16, 64, 16, 768, 8, 48, 256, 128

Offset

1,1

Links

Table of n, a(n) for n=1..44.

Catcon News.

Patrick De Geest, Repeated Factorisation of Concatenated Primefactors of the Composite Numbers.

Formula

a(n) = A000005(A019518(n)).

Example

The number of divisors of 2 is 2, so the first term is 2.
The number of divisors of 23 is 2, so the second term is 2.
The number of divisors of 235 is 4, so the third term is 4.

Mathematica

Table[DivisorSigma[0, FromDigits[Flatten[Table[IntegerDigits[Prime[j]], {j, 1, n}], 1]]], {n, 1, 100}] (* Labos Elemer, Mar 18 2005 *)

Crossrefs

Cf. A000005, A019518, A074809.

Sequence in context: A113416 A303140 A370469 * A173300 A181236 A280684

Adjacent sequences: A103175 A103176 A103177 * A103179 A103180 A103181

Keyword

nonn,base

Author

Parthasarathy Nambi, Mar 17 2005

Extensions

More terms from Labos Elemer, Mar 18 2005

Extended and edited by Charles R Greathouse IV, Apr 25 2010

Status

approved