Numbers k such that 8*10^k + 3*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056723
Numbers k such that 8*10^k + 3*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =7a(2) =23a(3) =29a(4) =133a(5) =173a(6) =367a(7) =1925a(8) =3707a(9) =5765a(10) =9709a(11) =19573a(12) =43753
External references
- oeis: A056723