Numbers k such that 21*2^k+1 is prime.

Terms

a(0) =1a(1) =4a(2) =5a(3) =7a(4) =9a(5) =12a(6) =16a(7) =17a(8) =41a(9) =124a(10) =128a(11) =129a(12) =187a(13) =209a(14) =276a(15) =313a(16) =397a(17) =899a(18) =1532a(19) =1613a(20) =1969a(21) =2245a(22) =2733a(23) =4585a(24) =4644a(25) =6712a(26) =6981a(27) =13344a(28) =17524a(29) =27124