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%I #3 Mar 30 2012 17:37:51
%S 1,2,3,3,4,4,4,5,5,6,4,4,5,5,6,6,6,5,5,6,6,7,7,7,7,8,5,5,6,6,7,7,7,7,
%T 8,8,8,5,5,6,6,7,7,7,7,8,8,8,8,8,6,6,7,7,8,8,8,8,9,9,9,9,9,9,10,6,6,7,
%U 7,8,8,8,8,9,9,9,9,9,9,10,10,10,7,7,8,8,9,9,9,9,10,10,10,10,10,10,11,11,11
%N Arrange binary trees in natural sequential order (see examples); sequence gives numbers of nodes.
%e The trees are x, (x,x), (x,(x,x)), ((x,x),x), ((x,x),(x,x)), (x,(x,(x,x))), ((x,(x,x)),x), ((x,x),(x,(x,x))), ((x,(x,x)),(x,x)), ((x,(x,x)),(x,(x,x))) (x,((x,x),x)), (((x,x),x),x), ((x,x)((x,x),x)), (((x,x),x),(x,x)), ((x,(xx)), ((x,x),x)),...
%Y Cf. A000108.
%K nonn,nice,easy
%O 1,2
%A Claude Lenormand (claude.lenormand(AT)free.fr), Jan 08 2001
%E More terms from _John W. Layman_, Feb 03 2003
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