Numbers k such that 3*10^k + 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

A102970

Numbers k such that 3*10^k + 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

    a(0) =2a(1) =3a(2) =6a(3) =12a(4) =36a(5) =39a(6) =44a(7) =90a(8) =258a(9) =512a(10) =1482a(11) =2378a(12) =2406a(13) =3224a(14) =3378a(15) =3876a(16) =4161a(17) =5510a(18) =7425a(19) =97242

External references