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
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