Numbers n with k digits such that n^2 == 1 (mod 10^k).

Terms

a(0) =1a(1) =9a(2) =49a(3) =51a(4) =99a(5) =249a(6) =251a(7) =499a(8) =501a(9) =749a(10) =751a(11) =999a(12) =1249a(13) =3751a(14) =4999a(15) =5001a(16) =6249a(17) =8751a(18) =9999a(19) =18751a(20) =31249a(21) =49999a(22) =50001a(23) =68751a(24) =81249a(25) =99999a(26) =218751a(27) =281249a(28) =499999a(29) =500001