Numbers n such that 9*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103105
Numbers n such that 9*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =0a(1) =2a(2) =4a(3) =41a(4) =53a(5) =64a(6) =197a(7) =238a(8) =784a(9) =3914a(10) =4436a(11) =12538a(12) =19036
External references
- oeis: A103105