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

Terms

a(0) =1a(1) =2a(2) =3a(3) =7a(4) =10a(5) =13a(6) =18a(7) =27a(8) =37a(9) =51a(10) =74a(11) =157a(12) =271a(13) =458a(14) =530a(15) =891a(16) =1723a(17) =1793a(18) =1849a(19) =1986a(20) =2191a(21) =2869a(22) =4993a(23) =7777a(24) =11730a(25) =15313a(26) =29171a(27) =35899a(28) =36227a(29) =71570