Numbers n such that 6*10^n + 3*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A103032

Numbers n such that 6*10^n + 3*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =1a(1) =2a(2) =4a(3) =7a(4) =18a(5) =19a(6) =23a(7) =24a(8) =34a(9) =41a(10) =56a(11) =64a(12) =84a(13) =149a(14) =272a(15) =755a(16) =1272a(17) =2398a(18) =2686a(19) =4800a(20) =5198a(21) =6217a(22) =8737a(23) =12388a(24) =12391a(25) =19702a(26) =42404

External references