Numbers n such that 4*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A102998

Numbers n such that 4*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =1a(1) =4a(2) =10a(3) =12a(4) =13a(5) =40a(6) =76a(7) =123a(8) =501a(9) =648a(10) =3541a(11) =4002a(12) =4228a(13) =5271a(14) =7432a(15) =27306a(16) =43402

External references