Numbers n such that 5*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103016
Numbers n such that 5*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =1a(1) =3a(2) =4a(3) =6a(4) =10a(5) =21a(6) =30a(7) =72a(8) =199a(9) =208a(10) =270a(11) =396a(12) =619a(13) =759a(14) =1077a(15) =1383a(16) =1566a(17) =1960a(18) =2653a(19) =3504a(20) =3786a(21) =6085a(22) =13110a(23) =36448a(24) =39582a(25) =47989a(26) =50998a(27) =66729
External references
- oeis: A103016