Numbers k such that 7*R_k - 60 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A256801
Numbers k such that 7*R_k - 60 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =4a(2) =11a(3) =23a(4) =86a(5) =148a(6) =191a(7) =232a(8) =271a(9) =656a(10) =844a(11) =1069a(12) =1318a(13) =1348a(14) =1411a(15) =2329a(16) =4120a(17) =4831a(18) =12691a(19) =14695a(20) =17719a(21) =39614a(22) =139417
External references
- oeis: A256801