Primes of the form 2^k + 15.

Terms

a(0) =17a(1) =19a(2) =23a(3) =31a(4) =47a(5) =79a(6) =271a(7) =1039a(8) =2063a(9) =4111a(10) =32783a(11) =65551a(12) =4194319a(13) =8388623a(14) =67108879a(15) =1073741839a(16) =4294967311