%I #14 Aug 01 2015 05:05:22

%S 17,14,5,7,13,106,11,158,927,314,6767,15,724317787,62,21,20,407,19,

%T 319,38,39,302,150698261,30,1055599,298,129,74

%N a(n) = least k such that the remainder when 18^k is divided by k is n.

%C 10^15 < a(29) <= 3612834616189533302730621726282897865691021. - _Max Alekseyev_, Apr 14 2012

%H Robert G. Wilson v, <a href="/A128158/a128158.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 < 3000000000, a = PowerMod[18, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t (* _Robert G. Wilson v_, Jun 23 2009 *)

%Y Cf. A036236, A078457, A119678, A119679, A127816, A119715, A119714, A127817, A127818, A127819, A127820, A127821, A128154, A128155, A128156, A128157, A128159, A128160, A128149, A128150.

%K hard,more,nonn

%O 1,1

%A _Alexander Adamchuk_, Feb 16 2007

%E a(13)-a(28) from _Robert G. Wilson v_, Jun 23 2009