Numbers k such that 3*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

a(0) =2a(1) =3a(2) =4a(3) =5a(4) =6a(5) =7a(6) =8a(7) =18a(8) =40a(9) =50a(10) =60a(11) =78a(12) =101a(13) =151a(14) =319a(15) =382a(16) =784a(17) =1732a(18) =1918a(19) =8855a(20) =11245a(21) =11960a(22) =12130a(23) =18533a(24) =22718a(25) =23365a(26) =24253a(27) =24549a(28) =25324a(29) =30178