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%I #5 Oct 23 2012 15:37:41
%S 1,3,7,16,33,70,141,287,578,1163,2327,4674,9349,18718,37452,74948,
%T 149897,299890,599781,1199724,2399498,4799278,9598557,19197792,
%U 38395600,76792313,153584811,307171904,614343809,1228692446,2457384893,4914778758,9829558241,19659134194,39318268464
%N A217941(n)/2.
%Y A217941 is the main entry.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Oct 23 2012