Numbers k such that 21^k - 2 is a prime.

Terms

a(0) =1a(1) =2a(2) =4a(3) =10a(4) =21a(5) =25a(6) =27a(7) =32a(8) =60a(9) =88a(10) =106a(11) =120a(12) =146a(13) =264a(14) =828a(15) =965a(16) =1944a(17) =4822a(18) =12089a(19) =14427a(20) =17354a(21) =42335a(22) =46395a(23) =58348a(24) =190632