Numbers k such that 4*R_k + 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099413
Numbers k such that 4*R_k + 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =4a(4) =10a(5) =20a(6) =26a(7) =722a(8) =1310a(9) =3170a(10) =28934a(11) =66284a(12) =67796a(13) =231254a(14) =338476
External references
- oeis: A099413