let rec f = function
    | n when (4 * n + 1) % n = 0 -> true
    | n when (4 * n + 3) % n = 0 -> false
    | n when (2 * n) % n = 0 -> f <| n / 2
    | _ -> raise BadArgumentException

[<EntryPoint>]
let main argv =
    printfn "%A" <| f 4
    0