%I A002185 M2233 N0885
%S A002185 3,1,11,43,19,683,2731,331,43691,174763,5419,2796203,251,87211,59,
%T A002185 715827883,67,281,1777,22366891,83,2932031007403,18837001,283,
%U A002185 4363953127297
%N A002185 Smallest primitive factor of 2^{2n+1} + 1.
%D A002185 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A002185 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002185 J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, 
               Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and 
               later supplements.
%D A002185 M. Kraitchik, Recherches sur la Th\'{e}orie des Nombres. Gauthiers-Villars, 
               Paris, Vol. 1, 1924, Vol. 2, 1929, see Vol. 2, p. 85.
%H A002185 J. Brillhart et al., <a href="http://www.ams.org/online_bks/conm22/">
               Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, 
               Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%H A002185 S. S. Wagstaff, Jr., <a href="http://www.cerias.purdue.edu/homes/ssw/
               cun/index.html">The Cunningham Project</a>
%Y A002185 Sequence in context: A008969 A119908 A153257 this_sequence A002589 A048522 
               A118020
%Y A002185 Adjacent sequences: A002182 A002183 A002184 this_sequence A002186 A002187 
               A002188
%K A002185 nonn
%O A002185 0,1
%A A002185 N. J. A. Sloane (njas(AT)research.att.com).