Numbers k for which R(k) + 3*10^floor(k/2) is prime, where R(k) = (10^k-1)/9 (repunit: A002275).
A331866
Numbers k for which R(k) + 3*10^floor(k/2) is prime, where R(k) = (10^k-1)/9 (repunit: A002275).
Terms
- a(0) =0a(1) =2a(2) =5a(3) =7a(4) =8a(5) =10a(6) =65a(7) =91a(8) =208a(9) =376a(10) =586a(11) =2744a(12) =3089a(13) =19378a(14) =20246
External references
- oeis: A331866