gistfile1.fs

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