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

A102938

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

Terms

    a(0) =1a(1) =3a(2) =4a(3) =7a(4) =12a(5) =51a(6) =87a(7) =123a(8) =198a(9) =202a(10) =537a(11) =831a(12) =1323a(13) =2508a(14) =2631a(15) =5568a(16) =6897a(17) =7524a(18) =9939a(19) =10674a(20) =11617a(21) =13257a(22) =14371a(23) =20176a(24) =36555a(25) =36874a(26) =40131a(27) =43125a(28) =58729a(29) =97044

External references