Numbers k such that 21^k + 2 is prime.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =7a(5) =24a(6) =40a(7) =112a(8) =310a(9) =1026a(10) =1286a(11) =36566a(12) =43717a(13) =53753