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%I #23 Jan 30 2023 15:01:07
%S 2,5,46,339,22,387497,11,535,10,111,38,8399,15,497,34,327,365,515,30,
%T 7219931,28,321,26,223793,44,10718597,242,35,2330,209,39,305,136,309,
%U 4382,10596486211,45,24751,7327,121,236,78821,55,4117,76,1751,30514339,83795,50,1333
%N a(n) = least k such that the remainder when 7^k is divided by k is n.
%H Robert G. Wilson v, <a href="/A119715/a119715.txt">Table of n, a(n) for n = 1..10000 with -1 for those entries where a(n) has not yet been found</a>
%t t = Table[0, {10000}]; k = 1; lst = {}; While[k < 4100000000, a = PowerMod[7, k, k]; If[ a<10001 && t[[a]]==0, t[[a]]=k; Print[{a,k}]]; k++ ]; t (* changed (to reflect the new limits) by _Robert G. Wilson v_, Jul 17 2009 *)
%t lk[n_]:=Module[{k=1},While[PowerMod[7,k,k]!=n,k++];k]; Array[lk,50] (* The program will take a long time to run. *) (* _Harvey P. Dale_, Jan 29 2023 *)
%Y Cf. A036236, A078457, A119678, A119679, A127816, A119714, A127817, A127818, A127819, A127820, A127821.
%K nonn
%O 1,1
%A _Ryan Propper_, Jun 12 2006
%E a(36) = 10596486211 and later terms from _Ryan Propper_, Feb 02 2007