Numbers n such that 6*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103043
Numbers n such that 6*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =3a(1) =5a(2) =15a(3) =47a(4) =69a(5) =123a(6) =713a(7) =2316a(8) =6147a(9) =8877a(10) =10704
External references
- oeis: A103043