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%I #10 Jul 07 2023 15:16:16
%S 1,1,2,1,3,3,2,3,3,3,5,4,3,4,3,4,4,4,2,2,3,4,3,4,4,5,2,5,3,6,5,5,7,7,
%T 7,4,4,6,4,9
%N Number of distinct prime factors of concatenation of first n primes.
%H Dario Alejandro Alpern, <a href="https://www.alpertron.com.ar/ECM.HTM">Factorization using the Elliptic Curve Method</a>.
%H Hisanori Mishima, <a href="https://www.asahi-net.or.jp/~KC2H-MSM/mathland/matha1/sm_prime.htm">Smarandache consecutive prime sequences (n = 1 to 100)</a>.
%e The number of distinct prime factors of 2 is 1 since it is a prime.
%e The number of distinct prime factors of 23 is 1 since it is a prime.
%e The number of distinct prime factors of 235 is 2.
%e The number of distinct prime factors of 2357 is 1 since it is a prime.
%t f[n_] := Length[ FactorInteger[ FromDigits[ Flatten[ Table[ IntegerDigits[ Prime[i]], {i, n}]] ]]]; Table[ f[n], {n, 15}] (* _Robert G. Wilson v_, Feb 22 2005 *)
%K nonn,base
%O 1,3
%A _Parthasarathy Nambi_, Feb 08 2005
%E More terms from _Robert G. Wilson v_, Feb 22 2005