1,3

Table of n, a(n) for n=1..31.

For n=12:

.....0..

.....00.

...0.000

..00000.

we can see nodes 7,8,9,10,11,12 ==> a(12) = 6

Sequence in context: A137580 A196369 A245710 * A157943 A267098 A304110

Adjacent sequences: A137509 A137510 A137511 * A137513 A137514 A137515

nonn

David Reiss (david.reiss(AT)utoronto.ca), May 11 2008

I think I managed to destroy the example by editing it. - N. J. A. Sloane, May 16 2008

approved