The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 9 07:17 EST 2022. Contains 358700 sequences. (Running on oeis4.)