Numbers n such that 6*10^n + 2*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103030
Numbers n such that 6*10^n + 2*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =7a(4) =16a(5) =39a(6) =229a(7) =352a(8) =433a(9) =766a(10) =2887a(11) =2976a(12) =10836a(13) =15097
External references
- oeis: A103030