Numbers n such that 6*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A103038

Numbers n such that 6*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) =1a(2) =3a(3) =4a(4) =10a(5) =22a(6) =40a(7) =54a(8) =81a(9) =84a(10) =106a(11) =193a(12) =597a(13) =681a(14) =1363a(15) =1876a(16) =4024a(17) =14163a(18) =18733a(19) =20842a(20) =23728a(21) =26419a(22) =31450a(23) =44694a(24) =64767

External references