OFFSET
1,5
COMMENTS
Is this sequence infinite?
a(9) > 10^11. - Tyler Busby, Feb 20 2023
EXAMPLE
a(1)=a(2)=a(3)=a(4)=1 since 2^2-1, 2^3-1, 2^5-1 and 2^7-1 are primes.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Jean-Louis Charton, Sep 13 2012
EXTENSIONS
a(7) from Jean-Louis Charton, Sep 18 2012
a(8) from Jean-Louis Charton, Oct 02 2012
STATUS
approved