Numbers n such that 6*10^n + 7*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103042
Numbers n such that 6*10^n + 7*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =0a(1) =2a(2) =156a(3) =1055a(4) =1997a(5) =8930a(6) =9563a(7) =19560a(8) =26838a(9) =63857
External references
- oeis: A103042