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%I #13 Jul 12 2015 20:35:36
%S 1,3,6,10669,9,18,3763,1010,20,35,2951,42,50,27,36,49,56,110,697,578,
%T 156,540923,70,287,104,147,4044,970,220,59378,119,345,66,3007,75,
%U 1990362,184,190,100,115,81,162,470,406,812,6631,105,310,160,207,322
%N Least positive number k such that 2^k mod k = 2n, or 0 if no such k exists.
%t lpn[n_]:=Module[{k=1},While[PowerMod[2,k,k]!=2n,k++];k]; Array[lpn,60,0] (* _Harvey P. Dale_, Jul 23 2012 *)
%Y A bisection of A036236: a(n) = A036236(2n).
%Y Cf. A124977.
%K nonn
%O 0,2
%A _N. J. A. Sloane_, May 11 2007, Jul 18 2008
%E New definition from _Benoit Jubin_, Jul 17 2008
%E More terms from _Max Alekseyev_, May 08 2009