Numbers n such that 4*10^n + 3*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A102988
Numbers n such that 4*10^n + 3*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =1a(1) =2a(2) =4a(3) =7a(4) =10a(5) =12a(6) =20a(7) =24a(8) =30a(9) =42a(10) =62a(11) =188a(12) =304a(13) =340a(14) =715a(15) =804a(16) =1040a(17) =1887a(18) =2079a(19) =2120a(20) =2260a(21) =2423a(22) =3319a(23) =5598a(24) =6072a(25) =22048a(26) =25713a(27) =28644a(28) =43353
External references
- oeis: A102988