Numbers n such that 5*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A103015

Numbers n such that 5*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =2a(1) =6a(2) =8a(3) =18a(4) =53a(5) =68a(6) =242a(7) =276a(8) =320a(9) =564a(10) =620a(11) =1782a(12) =2340a(13) =2454a(14) =5765a(15) =15530a(16) =15605a(17) =22938

External references