Disclaimer: Total F# Newbie question!
If I type the following into an F# file in Visual Studio
#light let squares = se
'seq' is a lazily-evaluated construct; it could be infinite, which is why FSI only shows the first few values. If you want to see it all, an easy thing to do is convert to a list, e.g.
printf "%A" (squares |> Seq.tolist)