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a(n) = least k such that the remainder when 17^k is divided by k is n.
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%I #8 Mar 31 2012 14:12:21

%S 2,3,7,13,142,11,25,9,10,299,57,203,46,69,274,613024059983,19,7099195,

%T 30,21,134,24065,38,133,28,27,205,155591,33,20452755522967,49,165,35,

%U 391,99,94271801,198,39,70,23353,62,2759,55,1623,122,22649,665,1591398755

%N a(n) = least k such that the remainder when 17^k is divided by k is n.

%H Robert G. Wilson v, <a href="/A128157/a128157.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 < 4500000000, a = PowerMod[17, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t

%Y Cf. A036236, A078457, A119678, A119679, A127816, A119715, A119714, A127817, A127818, A127819, A127820, A127821, A128154, A128155, A128156, A128158, A128159, A128160, A128149, A128150.

%K hard,nonn

%O 1,1

%A _Alexander Adamchuk_, Feb 16 2007

%E More terms from _Hagen von Eitzen_, Jul 31 2009

%E a(338) = 7615772967 = 3 * 11 * 230780999 [From _Daniel Morel_, May 18 2010]

%E a(100) = 36706228199, a(154) = 10618746241, a(444) = 10700153359, a(616) = 7969009427, a(720) = 11004291191, a(984) = 11601377453 [From _Daniel Morel_, Jun 15 2010]

%E a(184) = 16808380397, a(508) = 34412778035 [From _Daniel Morel_, Nov 05 2010]