pascal

let next L =
    let l1 = L |> List.pairwise |> List.map (fun (a,b) -> a + b )
    1::l1@[1]

next [1;3;3;1]

let pasc n =
    let rec pascrev (n:int): list<list<int>> =
        match n with
        | 1 -> [[1;1]]
        | _ -> match pascrev (n - 1) with
               | x::xs as prev-> (next x)::prev
    pascrev n |> List.rev

pasc 5