Numbers k such that exactly one of 2^k - 1 and 2^k + 1 is a prime.

Terms

a(0) =0a(1) =1a(2) =3a(3) =4a(4) =5a(5) =7a(6) =8a(7) =13a(8) =16a(9) =17a(10) =19a(11) =31a(12) =61a(13) =89a(14) =107a(15) =127a(16) =521a(17) =607a(18) =1279a(19) =2203a(20) =2281a(21) =3217a(22) =4253a(23) =4423a(24) =9689a(25) =9941a(26) =11213a(27) =19937a(28) =21701a(29) =23209