Numbers n such that 9*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A103100

Numbers n such that 9*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =0a(1) =3a(2) =6a(3) =18a(4) =30a(5) =88a(6) =93a(7) =154a(8) =177a(9) =228a(10) =573a(11) =897a(12) =981a(13) =1416a(14) =1450a(15) =3366a(16) =4932a(17) =5194a(18) =13479a(19) =18609a(20) =23346a(21) =51424a(22) =74676a(23) =80571

External references