OFFSET
1,2
EXAMPLE
1*(2^2-1)*(1*(2^2-1)+1)+1=13 prime, 2^2-1 first Mersenne prime, a(1)=1
2*(2^3-1)*(2*(2^3-1)+1)+1=211 prime, 2^3-1 second Mersenne prime, a(2)=2
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Pierre CAMI, Feb 22 2008
EXTENSIONS
a(27)-a(29) by Pierre CAMI, Oct 11 2014
STATUS
approved