a(9) = 6:
.
._._._._._._._._._. ._____._._._._____. ._._._._._._._._._.
| | | | | | | | | | |_____| | | |_____| | | | | | | | | | |
| | | | | | | | | | |_____| | | |_____| | | | | | | | | | |
|_|_|_|_|_|_|_|_|_| |_____|_|_|_|_____| |_|_|_|_|_|_|_|_|_|
| | | | | | | | | | |_____| | | |_____| |_____| | | |_____|
| | | | | | | | | | |_____| | | |_____| |_____| | | |_____|
|_|_|_|_|_|_|_|_|_| |_____|_|_|_|_____| |_____|_|_|_|_____|
| | | | | | | | | | |_____| | | |_____| | | | | | | | | | |
| | | | | | | | | | |_____| | | |_____| | | | | | | | | | |
|_|_|_|_|_|_|_|_|_| |_____|_|_|_|_____| |_|_|_|_|_|_|_|_|_|
| | | | | | | | | | |_____| | | |_____| |_____| | | |_____|
| | | | | | | | | | |_____| | | |_____| |_____| | | |_____|
|_|_|_|_|_|_|_|_|_| |_____|_|_|_|_____| |_____|_|_|_|_____|
.
._____._._._._____. ._____._._._._____. ._____._._._._____.
|_____| | | |_____| |_____| | | |_____| |_____| | | |_____|
| | | | | | | | | | |_____| | | |_____| |_____| | | |_____|
| | | |_|_|_| | | | | | | |_|_|_| | | | |_____|_|_|_|_____|
|_|_|_| | | |_|_|_| | | | | | | | | | | | | | | | | | | | |
|_____| | | |_____| |_|_|_| | | |_|_|_| | | | | | | | | | |
|_____|_|_|_|_____| |_____|_|_|_|_____| |_|_|_|_|_|_|_|_|_|
|_____| | | |_____| |_____| | | |_____| |_____| | | |_____|
| | | | | | | | | | |_____| | | |_____| |_____| | | |_____|
| | | |_|_|_| | | | | | | |_|_|_| | | | |_____|_|_|_|_____|
|_|_|_| | | |_|_|_| | | | | | | | | | | | | | | | | | | | |
|_____| | | |_____| |_|_|_| | | |_|_|_| | | | | | | | | | |
|_____|_|_|_|_____| |_____|_|_|_|_____| |_|_|_|_|_|_|_|_|_|
.
|