Numbers k such that 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099414
Numbers k such that 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =3a(2) =5a(3) =6a(4) =48a(5) =108a(6) =245a(7) =1044a(8) =20208a(9) =52740a(10) =89189a(11) =130080a(12) =183657a(13) =197061a(14) =348453
External references
- oeis: A099414