Numbers k such that 40*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056682
Numbers k such that 40*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =9a(4) =19a(5) =25a(6) =721a(7) =1309a(8) =3169a(9) =28933a(10) =66283a(11) =67795
External references
- oeis: A056682