Numbers k such that 7*10^k + 6*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

A103064

Numbers k such that 7*10^k + 6*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

    a(0) =1a(1) =7a(2) =90a(3) =93a(4) =125a(5) =147a(6) =498a(7) =868a(8) =879a(9) =1157a(10) =2958a(11) =3018a(12) =3317a(13) =3822a(14) =6948a(15) =8885a(16) =13092a(17) =33323a(18) =35847a(19) =79492

External references