Assertion: tree's root | /r/HasProperty | extra
Facets:
Source sentences:
text: Thus at each step one can either go down (append a (, 1) to the end) or go right (add one to the last number) (except the root, which is extra and can only go down), which shows the correspondence between the infinite binary tree and the above numbering; the sum of the entries (minus one) corresponds to the distance from the root, which agrees with the 2n−1 nodes at depth n − 1 in the infinite binary tree (2 corresponds to binary).