F# doesn't have an in-built iterate function, but found an equivalent on the F# Snippets site -- http://fssnip.net/18.

    let rec iterate f value = seq {
        yield value
        yield! iterate f (f value) }

Using the above we get ...

    let pascal = iterate (fun xs -> List.map2 (+) (0::xs) (xs @ [0])) [1]