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%I #7 Jul 31 2019 03:03:30
%S 2,1,1,2,4,9,20,44,97,230,540,1257,2920,7168,17393,41806,100408,
%T 250098,618124,1517008,3716627,9375710,23479016,58419236,145210076,
%U 368786352,931600246,2341625080,5877503872,15027036202,38225273720,96794415372
%N a(n) = Sum_{i=1..floor((n+2)/4)} a(2i-1)*a(n-2i+1), with a(1)=2 and a(2)=a(3)=1.
%K nonn
%O 1,1
%A _Clark Kimberling_
%E Offset corrected and title improved by _Sean A. Irvine_, Jul 30 2019