Numbers k such that 3*R_(k+2) + 10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A256458
Numbers k such that 3*R_(k+2) + 10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =4a(2) =5a(3) =6a(4) =11a(5) =26a(6) =92a(7) =98a(8) =110a(9) =215a(10) =232a(11) =354a(12) =522a(13) =648a(14) =1862a(15) =2322a(16) =2934a(17) =3797a(18) =6017a(19) =11236a(20) =24748a(21) =30011a(22) =37864a(23) =42904a(24) =57414a(25) =195478
External references
- oeis: A256458