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a(n) = Sum_{i=1..floor((n+2)/4)} a(2i-1)*a(n-2i+1), with a(1)=a(3)=2 and a(2)=1.
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%I #7 Jul 31 2019 03:03:23

%S 2,1,2,4,8,20,48,112,264,688,1760,4432,11136,30208,80160,209344,

%T 547584,1498752,4052224,10840064,28972416,80315136,220124160,

%U 597656576,1623036928,4522262528,12503194624,34330329088,94172397568,264205592576,735690285056

%N a(n) = Sum_{i=1..floor((n+2)/4)} a(2i-1)*a(n-2i+1), with a(1)=a(3)=2 and a(2)=1.

%K nonn

%O 1,1

%A _Clark Kimberling_

%E Offset corrected and title improved by _Sean A. Irvine_, Jul 30 2019