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%I #13 Apr 08 2024 06:54:42
%S 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,
%T 128,32,32,128,128,192,16,16,64,16,768,8,48,256,128
%N Number of divisors of the decimal concatenation of the first n primes.
%H <a href="http://catcon.sourceforge.net/pub/news/archives/000004.html">Catcon News</a>.
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/em_topic1.htm">Repeated Factorisation of Concatenated Primefactors of the Composite Numbers</a>.
%F a(n) = A000005(A019518(n)).
%e The number of divisors of 2 is 2, so the first term is 2.
%e The number of divisors of 23 is 2, so the second term is 2.
%e The number of divisors of 235 is 4, so the third term is 4.
%t Table[DivisorSigma[0, FromDigits[Flatten[Table[IntegerDigits[Prime[j]], {j, 1, n}], 1]]], {n, 1, 100}] (* _Labos Elemer_, Mar 18 2005 *)
%Y Cf. A000005, A019518, A074809.
%K nonn,base
%O 1,1
%A _Parthasarathy Nambi_, Mar 17 2005
%E More terms from _Labos Elemer_, Mar 18 2005
%E Extended and edited by _Charles R Greathouse IV_, Apr 25 2010