Numbers k such that 8*10^k + 7*R_k - 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A103090
Numbers k such that 8*10^k + 7*R_k - 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =7a(2) =36a(3) =99a(4) =325a(5) =1227a(6) =9261a(7) =9414a(8) =11115a(9) =25149a(10) =43212a(11) =95214
External references
- oeis: A103090