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%I #3 Mar 30 2012 16:50:48
%S 1,1,2,3,3,3,4,5,5,6,6,6,7,7,8,9,9,10,10,11,11,12,12,12,13,13,14,14,
%T 15,15,16
%N The number of nodes visible from underneath a binary tree, where the nodes are placed such that the innermost of the two sprouting nodes should be underneath the mother.
%e For n=12:
%e .....0..
%e .....00.
%e ...0.000
%e ..00000.
%e we can see nodes 7,8,9,10,11,12 ==> a(12) = 6
%K nonn
%O 1,3
%A David Reiss (david.reiss(AT)utoronto.ca), May 11 2008
%E I think I managed to destroy the example by editing it. - _N. J. A. Sloane_, May 16 2008
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