Numbers n such that 4*10^n + 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A102989
Numbers n such that 4*10^n + 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =1a(1) =3a(2) =5a(3) =6a(4) =8a(5) =15a(6) =26a(7) =53a(8) =60a(9) =97a(10) =183a(11) =205a(12) =302a(13) =396a(14) =456a(15) =467a(16) =607a(17) =828a(18) =1860a(19) =2743a(20) =4273a(21) =4781a(22) =5712a(23) =6038a(24) =6637a(25) =9222a(26) =10832a(27) =18865a(28) =25848a(29) =42247
External references
- oeis: A102989