Numbers k such that 2k-1 is prime.

Terms

a(0) =2a(1) =3a(2) =4a(3) =6a(4) =7a(5) =9a(6) =10a(7) =12a(8) =15a(9) =16a(10) =19a(11) =21a(12) =22a(13) =24a(14) =27a(15) =30a(16) =31a(17) =34a(18) =36a(19) =37a(20) =40a(21) =42a(22) =45a(23) =49a(24) =51a(25) =52a(26) =54a(27) =55a(28) =57a(29) =64