An interpretation of Motzkin numbers, the 21 paths from (0, 0) to (5, 0) using only steps northeast, east, and southeast, never dipping below the x-axis.
<a href="//commons.wikimedia.org/w/index.php?title=User:DJGrandfather&amp;action=edit&amp;redlink=1" class="new" title="User:DJGrandfather (page does not exist)">DJGrandfather</a>
<span class="int-own-work" lang="en">Own work</span>