Kth largest in BST

kthLargestBST.fs

type Node<'T> = 
    | Node of value: 'T * left: Node<'T> * right: Node<'T> 
    | Empty

let getKthLargest(root, n) =
    let rec loop = function
        | Empty -> Seq.empty
        | Node(value, left, right) -> 
            seq {
                yield! loop right          
                yield value
                yield! loop left
            }

    root |> loop |> Seq.item (n - 1)