login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A084680 Order of 10 modulo n [i.e., least m such that 10^m = 1 (mod n)] or 0 when no such number exists. 12
1, 0, 1, 0, 0, 0, 6, 0, 1, 0, 2, 0, 6, 0, 0, 0, 16, 0, 18, 0, 6, 0, 22, 0, 0, 0, 3, 0, 28, 0, 15, 0, 2, 0, 0, 0, 3, 0, 6, 0, 5, 0, 21, 0, 0, 0, 46, 0, 42, 0, 16, 0, 13, 0, 0, 0, 18, 0, 58, 0, 60, 0, 6, 0, 0, 0, 33, 0, 22, 0, 35, 0, 8, 0, 0, 0, 6, 0, 13, 0, 9, 0, 41, 0, 0, 0, 28, 0, 44, 0, 6, 0, 15, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,7
COMMENTS
When n is not divisible by 2 or 5, a(n) = A007732(n). A002329 contains the nonzero terms.
A number k > 0 appears in this sequence exactly A059892(k) times. - T. D. Noe, May 18 2007
LINKS
MAPLE
A084680 := proc(n) if gcd(n, 10) <> 1 then 0 ; elif n = 1 then 1 ; else numtheory[order](10, n) ; end if; end proc: seq(A084680(n), n=2..100) ; # R. J. Mathar, Mar 10 2010
MATHEMATICA
a[n_] := If[!CoprimeQ[n, 10], 0, MultiplicativeOrder[10, n]]; Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Nov 07 2012 *)
PROG
(PARI) a(n, b=10)=if(gcd(n, b)!=1, 0, znorder(Mod(b, n)));
vector(66, n, a(n)) \\ Joerg Arndt, Nov 15 2014
(GAP) List([1..100], n->OrderMod(10, n)); # Muniru A Asiru, Feb 26 2019
CROSSREFS
Sequence in context: A137378 A333275 A293071 * A051626 A357003 A264808
KEYWORD
nonn
AUTHOR
Lekraj Beedassy, Jun 30 2003
EXTENSIONS
More terms from John W. Layman, Aug 12 2003
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 19 06:21 EDT 2024. Contains 370953 sequences. (Running on oeis4.)