Numbers k such that 5*R_k + 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099418
Numbers k such that 5*R_k + 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =8a(2) =12a(3) =18a(4) =26a(5) =32a(6) =138a(7) =188a(8) =222a(9) =338a(10) =1002a(11) =2744a(12) =6530a(13) =38690a(14) =39464a(15) =335480a(16) =343734
External references
- oeis: A099418