Numbers n such that 8*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A103075

Numbers n such that 8*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

Terms

    a(0) =1a(1) =2a(2) =4a(3) =5a(4) =8a(5) =10a(6) =22a(7) =223a(8) =254a(9) =350a(10) =379a(11) =401a(12) =436a(13) =1154a(14) =1246a(15) =2053a(16) =2687a(17) =3725a(18) =4271a(19) =13096a(20) =21427a(21) =30266a(22) =36791a(23) =41759

External references