When you start out on F# your first thought might be: let square x = x * x let sumOfSquares n = [1..n] |> List.map square |> List.sum hey, that sort of looks like: public static class Utils { public static int SumOfSquares(int n) { return Enumerable.Range(1, n) .Select(i => i * i) .Sum(); } } Examples from F# for fun and profit: Sum of squares. At a first glance, F# looks sort like slightly different style of C#, where instead of using extension methods you[...]