Largest prime factor of the "repunit" number 11...1 (cf. A002275).

Terms

a(0) =11a(1) =37a(2) =101a(3) =271a(4) =37a(5) =4649a(6) =137a(7) =333667a(8) =9091a(9) =513239a(10) =9901a(11) =265371653a(12) =909091a(13) =2906161a(14) =5882353a(15) =5363222357a(16) =333667a(18) =27961a(19) =10838689a(20) =513239a(22) =99990001a(23) =182521213001a(24) =1058313049