Numbers k such that 2*10^k - 1 is prime.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =7a(5) =26a(6) =27a(7) =53a(8) =147a(9) =236a(10) =248a(11) =386a(12) =401a(13) =546a(14) =785a(15) =1325a(16) =1755a(17) =2906a(18) =3020a(19) =5407a(20) =5697a(21) =5969a(22) =7517a(23) =15749a(24) =19233a(25) =38232a(26) =55347a(27) =1059002