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

Author

Parthasarathy Nambi, Mar 17 2005

Keywords

• nonn
• base

Examples

			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.
		

Links

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

Crossrefs

Cf. A000005, A019518, A074809.

Programs

Mathematica

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

Formula

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

Extensions

More terms from Labos Elemer, Mar 18 2005

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