Numbers n for which 4*R_n - 1 is a prime, where R_n = 11...1 is the repunit (A002275) of length n.
A096845
Numbers n for which 4*R_n - 1 is a prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =1a(1) =2a(2) =3a(3) =6a(4) =9a(5) =12a(6) =30a(7) =32a(8) =183a(9) =297a(10) =492a(11) =41316
External references
- oeis: A096845