Numbers k such that 7*R_k + 3*10^k - 4 is prime, where R_k = 11...11 is the repunit (A002275) of length k.

A259125

Numbers k such that 7*R_k + 3*10^k - 4 is prime, where R_k = 11...11 is the repunit (A002275) of length k.

Terms

    a(0) =2a(1) =14a(2) =54a(3) =68a(4) =84a(5) =86a(6) =156a(7) =2766a(8) =3380a(9) =3876a(10) =5208a(11) =10746a(12) =15768a(13) =31316a(14) =40958a(15) =45804a(16) =46566a(17) =51008a(18) =80162

External references