Numbers k such that 40*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056681
Numbers k such that 40*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =3a(2) =10a(3) =27a(4) =54a(5) =93a(6) =474a(7) =2079a(8) =4834a(9) =5844a(10) =12337a(11) =20193a(12) =49528a(13) =56988a(14) =71545a(15) =77308
External references
- oeis: A056681