Least number m such that 10^m == +- 1 mod (10n + 1).

Terms

a(0) =1a(1) =6a(2) =15a(3) =5a(4) =16a(5) =30a(6) =35a(7) =9a(8) =3a(9) =2a(10) =3a(11) =11a(12) =65a(13) =46a(14) =75a(15) =33a(16) =18a(17) =90a(18) =95a(19) =33a(20) =15a(21) =48a(22) =6a(23) =15a(24) =25a(25) =28a(26) =5a(27) =14a(28) =96a(29) =42