Numbers n such that 4*10^n + 5*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A102992

Numbers n such that 4*10^n + 5*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =1a(1) =2a(2) =4a(3) =5a(4) =13a(5) =22a(6) =25a(7) =28a(8) =38a(9) =67a(10) =142a(11) =284a(12) =295a(13) =380a(14) =397a(15) =1217a(16) =1640a(17) =2885a(18) =3286a(19) =7735a(20) =29306

External references