0 together with numbers k such that 4*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099412
0 together with 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) =2a(2) =4a(3) =11a(4) =28a(5) =55a(6) =94a(7) =475a(8) =2080a(9) =4835a(10) =5845a(11) =12338a(12) =20194a(13) =49529a(14) =56989a(15) =71546a(16) =77309a(17) =284330
External references
- oeis: A099412