Numbers k such that 2*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099410
Numbers k such that 2*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =2a(2) =3a(3) =5a(4) =14a(5) =176a(6) =416a(7) =2505a(8) =2759a(9) =7925a(10) =9401a(11) =10391a(12) =12105a(13) =19616a(14) =261704a(15) =264539
External references
- oeis: A099410