code: func MerkleNodeIndex(depth, width, treeDepth uint64) uint64 {
  	return merkleNodeIndexTraverse(0, depth, width, treeDepth)
  }
docs: // MerkleNodeIndex indexes a given node in the tree.
  // 	depth is the depth of the node, counting from root
  // 	width is the width of the node, counting from left
  // 	treeDepth is the depth of whole tree