let isPrime n =

    let rec check i =

        i > n/2 || (n % i <> 0 && check (i + 1))

    check 2

​

let nums = [ 16; 17; 3; 4; 2; 5; 11; 6; 7; 18; 13; 14; ]

​

let listPrime lst =

    lst |> List.filter isPrime

​

nums |> listPrime |> printfn "%A"

​