gistfile1.fs

let rec primesIn (ns: int list) (x: int) =     
    let newList = 
        (List.choose (fun y -> 
            match y with
                | y when (y % x = 0) -> None
                | _ -> Some y) ns)
    if newList.[0]*newList.[0] <= newList.[newList.Length-1] then
        x :: primesIn newList newList.[0]
    else x :: newList