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a(n) = least k such that the remainder when 11^k is divided by k is n.
38

%I #36 Apr 24 2016 12:03:35

%S 2,3,118,7,39,155,38,9,14,18659,13,8153,92,1317,106,35,26,49,34,57,68,

%T 253,327,1271,28,27,94,1633,46,161,415,1141,44,909589,86,161015,119,

%U 1293,82,673279,129,577679,4578,77,164,65,74,3589,76,147,115

%N a(n) = least k such that the remainder when 11^k is divided by k is n.

%H Daniel Morel, <a href="/A127819/b127819.txt">Table of n, a(n) for n = 1..189</a>

%H Daniel Morel, Robert G. Wilson v et al., <a href="/A127819/a127819_1.txt">Table of n, a(n) for n = 1..10000 with -1 for large entries where a(n) has not yet been found</a>

%t t = Table[0, {10000} ]; k = 1; While[ k < 4300000000, a = PowerMod[11, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t

%t f[n_]:=Module[{k=1},While[PowerMod[11,k,k]!=n,k++];k]; Array[f,51] (* _Harvey P. Dale_, Mar 12 2013 *)

%Y Cf. A036236, A078457, A119678, A119679, A127816, A119715, A119714, A127817, A127818, A127820, A127821.

%K nonn

%O 1,1

%A _Alexander Adamchuk_, Jan 30 2007

%E a(52) from _Max Alekseyev_ & Joe K. Crump (joecr(AT)carolina.rr.com), Feb 06 2007

%E a(108), a(514), a(754), a(808), a(820), a(880), a(934), a(948) added by _Daniel Morel_, May 18 2010, Jun 17 2010

%E a-file updated by _Max Alekseyev_, Dec 10 2010

%E a(112), a(348), a(810) added by _Daniel Morel_, Mar 12 2015