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

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A084681 Order of 10 modulo 9n [i.e., least m such that 10^m = 1 (mod 9n)] or 0 when no such number exists. 4
 1, 0, 3, 0, 0, 0, 6, 0, 9, 0, 2, 0, 6, 0, 0, 0, 16, 0, 18, 0, 6, 0, 22, 0, 0, 0, 27, 0, 28, 0, 15, 0, 6, 0, 0, 0, 3, 0, 6, 0, 5, 0, 21, 0, 0, 0, 46, 0, 42, 0, 48, 0, 13, 0, 0, 0, 18, 0, 58, 0, 60, 0, 18, 0, 0, 0, 33, 0, 66, 0, 35, 0, 8, 0, 0, 0, 6, 0, 13, 0, 81, 0, 41, 0, 0, 0, 84, 0, 44, 0, 6, 0, 15, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 K. Matthews, Finding the order of a (mod m) FORMULA From Robert Israel, Feb 22 2019: (Start) a(n) = A084680(9*n). If n is not divisible by 3, a(n) = A084680(n). Otherwise a(n) can be either A084680(n), 3*A084680(n) or 9*A084680(n). (End) MAPLE f:= proc(n) if igcd(n, 10)>1 then 0 else numtheory:-order(10, 9*n) fi end proc: map(f, [\$1..100]); # Robert Israel, Feb 22 2019 MATHEMATICA a[n_] := If[GCD[10, 9n] != 1, 0, MultiplicativeOrder[10, 9n]]; Array[a, 100] (* Jean-François Alcover, Jul 19 2020 *) PROG (PARI) a(n) = if (gcd(10, 9*n) != 1, 0, znorder(Mod(10, 9*n))); \\ Michel Marcus, Feb 23 2019 (GAP) List([1..100], n->OrderMod(10, 9*n)); # Muniru A Asiru, Feb 26 2019 CROSSREFS Cf. A084680, A190301, A216479. Sequence in context: A181189 A327889 A221702 * A261038 A285852 A096528 Adjacent sequences: A084678 A084679 A084680 * A084682 A084683 A084684 KEYWORD nonn AUTHOR Lekraj Beedassy, Jun 30 2003 EXTENSIONS More terms from John W. Layman, Oct 09 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.

Last modified November 26 21:15 EST 2022. Contains 358362 sequences. (Running on oeis4.)