Numbers k such that 2*10^k + 4*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A102952
Numbers k such that 2*10^k + 4*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =3a(2) =6a(3) =11a(4) =30a(5) =128a(6) =183a(7) =375a(8) =2159a(9) =2568a(10) =3369a(11) =24989a(12) =38810a(13) =59558a(14) =74874
External references
- oeis: A102952