A003566 Least number m such that 10^m == +- 1 mod (10n + 1).

1, 6, 15, 5, 16, 30, 35, 9, 3, 2, 3, 11, 65, 46, 75, 33, 18, 90, 95, 33, 15, 48, 6, 15, 25, 28, 5, 14, 96, 42, 155, 53, 55, 30, 6, 171, 78, 42, 176, 100, 8, 70, 215, 42, 10, 230, 78, 6, 245, 166, 24, 26, 58, 270, 252, 16, 285, 246, 98, 150, 69, 66, 315, 16, 30

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..10000 (first 1000 terms from Harvey P. Dale)

Programs

Mathematica

lnm[n_]:=Module[{m=1},While[!MemberQ[{1,10n},PowerMod[10,m,10n+1]],m++];m]; Array[lnm,60] (* Harvey P. Dale, Feb 12 2022 *)