Primes of the form 2^k + 9.

Terms

a(0) =11a(1) =13a(2) =17a(3) =41a(4) =73a(5) =137a(6) =521a(7) =1033a(8) =262153a(9) =8388617a(10) =1073741833a(11) =137438953481