Numbers k such that 5*10^k + 2*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A103011
Numbers k such that 5*10^k + 2*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =5a(2) =11a(3) =14a(4) =62a(5) =74a(6) =107a(7) =110a(8) =121a(9) =128a(10) =139a(11) =320a(12) =2956a(13) =11116
External references
- oeis: A103011