Numbers k such that 5*R_k + 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099417
Numbers k such that 5*R_k + 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =4a(4) =6a(5) =10a(6) =15a(7) =22a(8) =88a(9) =207a(10) =528a(11) =960a(12) =2100a(13) =18522a(14) =36783a(15) =38517
External references
- oeis: A099417