0,16

Each connected group of unoccupied lines in the hexagonal structure enclosed by toothpicks counts as a hole.

Olaf Voß, Table of n, a(n) for n = 0..625

N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS

Olaf Voß, Visualisation of the structure

Index entries for sequences related to toothpick sequences

Structure after step 8:

\_/

\_/ \_/

\_/ \_/ \_/

\_/ _/ \_ \_/

/ \_/ \_/ \_/ \

\_/ \_/ \_/ \_/

/ \ / \_/ \ / \

/ \_ \_/ _/ \

/ \_/ \_/ \

/ \_/ \

/ \

There are 6 holes in this structure, in each 1 toothpick is missing (size=1), so a(8)=1.

For number of holes see A184408.

Sequence in context: A032552 A087717 A053444 * A243129 A135717 A079083

Adjacent sequences: A175794 A175795 A175796 * A175798 A175799 A175800

nonn

Olaf Voß, Jan 13 2011

approved