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A109799
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Primes p such that 2^p - 1 is a Chen prime. 2^p - 1 is then called a Mersenne Chen prime.
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1
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OFFSET
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1,1
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COMMENTS
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Conjecture: 2^127 - 1 is the largest Mersenne Chen prime.
Except for the initial term 2, this sequence is the intersection of A000043 and A000978. [From Max Alekseyev, Oct 28 2008]
First 10 members equals A152961. [From Omar E. Pol, Dec 20 2008]
Except for the initial term 2, this sequence coincides with A107360. [From Max Alekseyev, Jan 28 2010]
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LINKS
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Table of n, a(n) for n=1..10.
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EXAMPLE
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a(5)=13 because 2^13 - 1 = 8191 is prime and 2^13 + 1 = 3*2731 is semiprime.
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CROSSREFS
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Cf. A000043, A109611.
Cf. A152961. [From Omar E. Pol, Dec 20 2008]
Sequence in context: A120857 A233516 A000043 * A152961 A109461 A138539
Adjacent sequences: A109796 A109797 A109798 * A109800 A109801 A109802
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KEYWORD
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hard,more,nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Aug 15 2005
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STATUS
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approved
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