Numbers k such that 2^k + 1 is the product of two distinct primes.

Terms

a(0) =5a(1) =6a(2) =7a(3) =11a(4) =12a(5) =13a(6) =17a(7) =19a(8) =20a(9) =23a(10) =28a(11) =31a(12) =32a(13) =40a(14) =43a(15) =61a(16) =64a(17) =79a(18) =92a(19) =101a(20) =104a(21) =127a(22) =128a(23) =148a(24) =167a(25) =191a(26) =199a(27) =256a(28) =313a(29) =347