Numbers k such that 2*10^k + R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056700
Numbers k such that 2*10^k + R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =2a(2) =3a(3) =12a(4) =18a(5) =23a(6) =57a(7) =128a(8) =543a(9) =584a(10) =833a(11) =2450a(12) =2810a(13) =2873a(14) =3671a(15) =6384a(16) =10296a(17) =16704a(18) =53049a(19) =56544a(20) =74253
External references
- oeis: A056700