OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)
FORMULA
MATHEMATICA
Table[Length[Union[PowerMod[10, Range[0, n], n]]], {n, 100}] (* T. D. Noe, Aug 30 2006 *)
a[n_] := Module[{e = IntegerExponent[n, {2, 5}]}, Max[e] + MultiplicativeOrder[10, n/Times @@ ({2, 5}^e)]]; Array[a, 100] (* Amiram Eldar, Aug 25 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Henry Bottomley, Apr 20 2000
STATUS
approved