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A072677
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a(n) = prime(prime(n)+1) where prime(k) is the k-th prime.
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13
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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
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OFFSET
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1,1
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COMMENTS
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Prime numbers q for which the number of prime numbers smaller than q is also a prime number.
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LINKS
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EXAMPLE
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a(4)=prime(prime(4)+1), prime(4)=7, hence a(4)=prime(8)=19.
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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MAPLE
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with(numtheory): seq(ithprime(ithprime(i)+1), i=1..51);
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MATHEMATICA
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PROG
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Mark Hudson (mrmarkhudson(AT)hotmail.com), Jul 05 2002
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EXTENSIONS
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STATUS
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approved
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