OFFSET
1,1
EXAMPLE
M(1)=2^2-1=3, (3*3)^2 + 3*3 -1 = 89 prime so a(1)=3
M(2)=2^3-1=7, (3*7)^2 + 3*7 -1 = 461 prime so a(2)=3
M(3)=2^5-1=31, (3*31)^2 + 3*31 -1 = 8741 prime so a(3)=3
M(4)=2^7-1=127,(7*127)^2 + 7*127 -1 = 791209 prime so a(4)=7
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Pierre CAMI, Jun 10 2005
EXTENSIONS
More terms from Pierre CAMI, Nov 21 2011
STATUS
approved