Numbers k such that 90*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056662
Numbers k such that 90*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =16a(4) =139a(5) =989a(6) =1886a(7) =3529a(8) =5995a(9) =13819a(10) =21872a(11) =26044a(12) =87719a(13) =232598
External references
- oeis: A056662