OFFSET
1,1
EXAMPLE
a(1) = 2 is a term since it is a prime and 2^2 - 1 = 3 and 2*2 - 1 = 3 are primes.
a(2) = 3 is a term since it is a prime and 2^3 - 1 = 7 and 2*3 - 1 = 5 are primes.
MATHEMATICA
Select[MersennePrimeExponent[Range[47]], PrimeQ[2# -1] &] (* Amiram Eldar, Jul 29 2020 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Juri-Stepan Gerasimov, Feb 03 2010, Feb 06 2010
EXTENSIONS
a(9)-a(11) from Robert G. Wilson v, Feb 26 2010
STATUS
approved