Divisors of the repunit 111111111111 = A002275(12).

Terms

a(0) =1a(1) =3a(2) =7a(3) =11a(4) =13a(5) =21a(6) =33a(7) =37a(8) =39a(9) =77a(10) =91a(11) =101a(12) =111a(13) =143a(14) =231a(15) =259a(16) =273a(17) =303a(18) =407a(19) =429a(20) =481a(21) =707a(22) =777a(23) =1001a(24) =1111a(25) =1221a(26) =1313a(27) =1443a(28) =2121a(29) =2849