%I A127817
%S A127817 2,7,6,5,38,723,74,2592842671511,11,3827,14,717,34,59035,21,259,152,237,
%T A127817 62,626131,30,169,58,25,56,1921,39,361,65,49,63010,287,48,55,46,63,932,
%U A127817 3786791,69,69637,230,221,6707,1057,57,4907,253,681,148,393217991,70
%N A127817 a(n) = least k such that the remainder when 9^k is divided by k is n.
%H A127817 Robert G. Wilson v; corrected by Mark Forbes, Oct 25 2009; <a href="a127817.txt">
               Table of n, a(n) for n = 1..10000 with -1 for those entries where 
               a(n) has not yet been found</a>
%p A127817 a127817 := [seq(0,j=1..nmax)] ; for k from 1 do n := modp(9^k,k) ; if 
               n > 0 and n <= nmax then if op(n,a127817) = 0 then a127817 := subsop(n=k,
               a127817) ; print( op(1..50,a127817) ) ; fi; fi; od: [From R. J. Mathar 
               (mathar(AT)strw.leidenuniv.nl), Jul 16 2009]
%t A127817 t = Table[0, {10000}]; k = 1; lst = {}; While[k < 4500000000, a = PowerMod[9, 
               k, k]; If[ a<10001 && t[[a]]==0, t[[a]]=k; Print[{a,k}]]; k++ ]; 
               t
%Y A127817 Cf. A036236, A078457, A119678, A119679, A127816, A119715, A119714, A127818, 
               A127819, A127820, A127821.
%Y A127817 Sequence in context: A074067 A110988 A047224 this_sequence A047232 A103557 
               A158241
%Y A127817 Adjacent sequences: A127814 A127815 A127816 this_sequence A127818 A127819 
               A127820
%K A127817 hard,nonn
%O A127817 1,1
%A A127817 Alexander Adamchuk (alex(AT)kolmogorov.com), Jan 30 2007
%E A127817 a(8) <= 2592842671511 from Joe K. Crump (joecr(AT)carolina.rr.com), Feb 
               06 2007
%E A127817 I changed the Mathematica coding to reflect the current limits Robert 
               G. Wilson v (rgwv(AT)rgwv.com), Jul 18 2009
%E A127817 Value for a(8) as suggested by J. K. Crump confirmed by Hagen von Eitzen 
               (math(AT)von-eitzen.de), Jul 21 2009
%E A127817 Corrected authorship of a-file - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Aug 24 2009