Numbers k such that 9*R_(k+2) - 5*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A257038
Numbers k such that 9*R_(k+2) - 5*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =3a(1) =192a(2) =1133a(3) =4763a(4) =5812a(5) =48467a(6) =130620a(7) =466002
External references
- oeis: A257038