Primes of the form 3*2^k - 25.

Terms

a(0) =23a(1) =71a(2) =167a(3) =359a(4) =743a(5) =1511a(6) =12263a(7) =24551a(8) =196583a(9) =393191a(10) =786407a(11) =6291431a(12) =25165799a(13) =1610612711a(14) =6442450919a(15) =25769803751a(16) =103079215079a(17) =206158430183