Numbers k such that 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099422
Numbers k such that 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =2a(2) =3a(3) =5a(4) =8a(5) =9a(6) =15a(7) =51a(8) =71a(9) =77a(10) =224a(11) =296a(12) =315a(13) =2090a(14) =2906a(15) =3395a(16) =3882a(17) =5114a(18) =6056a(19) =7254a(20) =7995a(21) =18173a(22) =18971a(23) =35006a(24) =69674a(25) =175428a(26) =253313
External references
- oeis: A099422