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A117249
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Prime numbers n for which the number of prime numbers smaller than n is also a prime number.
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0
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5, 7, 13, 19, 37, 43, 61, 71, 89, 113, 131, 163, 181, 193, 223, 251, 281, 293, 337, 359, 373, 409, 433, 463, 521, 557, 569, 593, 601, 619, 719, 743, 787, 809, 863, 881, 929, 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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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FORMULA
| a(n) = prime(1 + prime(n)). - T. D. Noe, April 05 2011
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EXAMPLE
| 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.
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MATHEMATICA
| Prime[1 + Prime[Range[100]]] (* From Harvey P. Dale, Apr 05 2011 *)
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CROSSREFS
| Cf. A000720.
Sequence in context: A006512 A074304 A072677 * A063910 A189557 A045444
Adjacent sequences: A117246 A117247 A117248 * A117250 A117251 A117252
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KEYWORD
| nonn
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AUTHOR
| Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006
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EXTENSIONS
| Corrected and extended by Harvey P. Dale, Apr 05 2011.
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