Numbers n such that 9*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103094
Numbers n such that 9*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =5a(1) =29a(2) =60a(3) =147a(4) =186a(5) =456a(6) =678a(7) =1373a(8) =3378a(9) =15726a(10) =68231
External references
- oeis: A103094