Numbers k such that 7*10^k + 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A103059
Numbers k such that 7*10^k + 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =4a(2) =7a(3) =34a(4) =82a(5) =451a(6) =772a(7) =2554a(8) =6250a(9) =15137a(10) =20074a(11) =37378a(12) =53068
External references
- oeis: A103059