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

A103000

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

Terms

    a(0) =0a(1) =3a(2) =4a(3) =6a(4) =10a(5) =12a(6) =18a(7) =40a(8) =48a(9) =96a(10) =106a(11) =114a(12) =144a(13) =364a(14) =618a(15) =1090a(16) =11370a(17) =59454a(18) =196684

External references