A007736 - OEIS

%I #29 Jul 10 2024 20:31:56

%S 1,1,2,1,1,2,6,2,6,1,5,2,4,6,2,4,16,6,9,1,6,5,22,2,1,4,18,6,14,2,3,8,

%T 10,16,6,6,36,9,4,2,20,6,42,5,6,22,46,4,42,1,16,4,52,18,5,6,18,14,29,

%U 2,30,3,6,16,4,10,22,16,22,6,5,6,72,36,2,9,30,4,39,4,54,20,82,6,16,42,14,10,44

%N Period of repeating digits of 1/n in base 5.

%H T. D. Noe, <a href="/A007736/b007736.txt">Table of n, a(n) for n=1..1000</a>

%H <a href="/index/1#1overn">Index entries for sequences related to decimal expansion of 1/n</a>

%t f[n_] := MultiplicativeOrder[5, n/(5^IntegerExponent[n, 5])]; Array[f, 80] (* _Robert G. Wilson v_, Jun 10 2011 *)

%t Table[Length[RealDigits[1/n,5][[1,1]]],{n,90}]/.(0->1) (* _Harvey P. Dale_, Dec 28 2016 *)

%o (PARI) A007736(n,bas)={ local(p) ; for(sp=2,1000000, for(s=1,sp-1, p=sp-s ; if( ((bas^p-1)*bas^s) % n == 0, return(p) ; ) ; ) ; ) ; return(-1) ; } { for(n=1,100, print(n," ",A007736(n,5)) ; ) ; } \\ _R. J. Mathar_, Aug 30 2006

%o (PARI) a(n)=znorder(Mod(5,n/5^valuation(n,5))) \\ _Charles R Greathouse IV_, Jun 10 2011

%K nonn,base

%O 1,3

%A _N. J. A. Sloane_, Hal Sampson (hals(AT)easynet.com), _David W. Wilson_