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 A117249 Prime numbers n for which the number of prime numbers smaller than n is also a prime number. 0

%I

%S 5,7,13,19,37,43,61,71,89,113,131,163,181,193,223,251,281,293,337,359,

%T 373,409,433,463,521,557,569,593,601,619,719,743,787,809,863,881,929,

%U 971,997,1033,1069,1091,1163,1181,1213,1223,1301,1423,1439,1451,1481,1511,1531,1601,1627,1693,1733,1747,1789,1831,1861,1931

%N Prime numbers n for which the number of prime numbers smaller than n is also a prime number.

%F a(n) = prime(1 + prime(n)). - T. D. Noe, April 05 2011

%e 163 is in the sequence because (1) it is a prime number, (2) there are 37 prime numbers smaller than 163 and 37 is also a prime number.

%t Prime[1 + Prime[Range[100]]] (* From Harvey P. Dale, Apr 05 2011 *)

%Y Cf. A000720.

%K nonn

%O 0,1

%A Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006

%E Corrected and extended by Harvey P. Dale, Apr 05 2011.

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