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A137512
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.
0
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, 15, 15, 16
OFFSET
1,3
EXAMPLE
For n=12:
.....0..
.....00.
...0.000
..00000.
we can see nodes 7,8,9,10,11,12 ==> a(12) = 6
CROSSREFS
Sequence in context: A340068 A196369 A245710 * A157943 A267098 A304110
KEYWORD
nonn
AUTHOR
David Reiss (david.reiss(AT)utoronto.ca), May 11 2008
EXTENSIONS
I think I managed to destroy the example by editing it. - N. J. A. Sloane, May 16 2008
STATUS
approved