BinaryTreeParentArray from BinaryTree
A binary tree as its parent array: its nodes numbered in order, entry k the number of the k-th node's parent, 0 at the root.
An order isomorphism: the k-th tree BinaryTrees lists goes to the k-th array BinaryTreeParentArrays lists.
Called as CombinatorialMap(x, "BinaryTreeParentArray"). The head's page has its examples.