Numbers k such that 3*R_k - 20 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A256772
Numbers k such that 3*R_k - 20 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =3a(2) =4a(3) =7a(4) =9a(5) =37a(6) =39a(7) =67a(8) =73a(9) =183a(10) =216a(11) =1161a(12) =2622a(13) =2775a(14) =6240a(15) =22078a(16) =30384a(17) =189385
External references
- oeis: A256772