Numbers n such that 4*10^n + R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A102981
Numbers n such that 4*10^n + R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =1a(1) =4a(2) =5a(3) =13a(4) =31a(5) =55a(6) =58a(7) =59a(8) =61a(9) =79a(10) =91a(11) =103a(12) =121a(13) =196a(14) =229a(15) =9439a(16) =13051a(17) =22960a(18) =31297
External references
- oeis: A102981