OFFSET
1,1
COMMENTS
Sequence is based on the following (false) conjecture Shanks mentions in his paper (p.6), which someone else made: "If M_p1 and M_p2 are successive Mersenne primes, their arithmetic mean is also prime." The first four values in the sequence are prime, while the rest up to (2^756839-1 + 2^216091-1)/2 are not. Conjecture: there are no more primes in this sequence after 4159.
LINKS
D. Shanks, Squfof Notes
EXAMPLE
a(3)=79 because (31+127)/2 = 79.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Oct 24 2004
STATUS
approved