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A109799 Primes p such that 2^p - 1 is a Chen prime. 1
2, 3, 5, 7, 13, 17, 19, 31, 61, 127 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For p in this sequence, 2^p - 1 is called a Mersenne-Chen prime.

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 given by A107360. - Max Alekseyev, Oct 28 2008, Jan 28 2010

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

a(5)=13 because 2^13 - 1 = 8191 is prime and 2^13 + 1 = 3*2731 is semiprime.

CROSSREFS

Cf. A000043, A109611.

First 10 members equals A152961. - Omar E. Pol, Dec 20 2008

Sequence in context: A120857 A233516 A000043 * A152961 A109461 A138539

Adjacent sequences:  A109796 A109797 A109798 * A109800 A109801 A109802

KEYWORD

hard,more,nonn

AUTHOR

Jason Earls, Aug 15 2005

STATUS

approved

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Last modified October 19 11:43 EDT 2018. Contains 316359 sequences. (Running on oeis4.)