OFFSET
1,1
COMMENTS
a(15)=87888967 but a(14) is unknown. - Jeppe Stig Nielsen, Mar 17 2018
The prime pair related to a(14) was found four days ago, and today double checking has proved that they are indeed the first occurrence for n=14. - Jeppe Stig Nielsen, May 02 2018
LINKS
David Broadhurst, Posting to PrimeForm list.
David Broadhurst, Chris Caldwell and others, GFN near mid-air collision, digest of 16 messages in primeform Yahoo group, May 2 - May 5, 2006. [Cached copy]
Yves Gallot's compilation of generalized Fermat primes.
FORMULA
a(n) is the smallest number such that (a(n)+1)^(2^n)+1 and (a(n)-1)^(2^n)+1 are both prime.
a(n) = A217993(n) + 1. - Jeppe Stig Nielsen, Feb 27 2016
EXAMPLE
a(11)=6992033 because 6992034^2048+1 is prime, 6992032^2048+1 is prime and no smaller pair of bases differing by 2 gives a pair of primes with the exponent 2^11=2048.
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
David Broadhurst, May 06 2006
EXTENSIONS
a(13) from Jeppe Stig Nielsen, Mar 17 2018
a(14) and a(15) from Jeppe Stig Nielsen, May 02 2018
STATUS
approved