Numbers k such that 7*10^k + 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A103066
Numbers k such that 7*10^k + 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =6a(4) =60a(5) =288a(6) =1314a(7) =1728a(8) =2493a(9) =13893a(10) =13944a(11) =17100a(12) =70227
External references
- oeis: A103066