Numbers k such that 80*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056664
Numbers k such that 80*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =18a(2) =78a(3) =138a(4) =222a(5) =462a(6) =543a(7) =1095a(8) =1418a(9) =3246a(10) =3876a(11) =4416a(12) =9506a(13) =11090a(14) =14601a(15) =27810a(16) =29187
External references
- oeis: A056664