FizzBuzz.fs

let is divisor outputString n result =
    if n % divisor = 0 then
        Some ( (result |> Option.defaultValue("")) + outputString)
    else if result.IsSome then
        result
    else
        None

let fizz x s = is 3 "fizz" x s
let buzz x s = is 5 "buzz" x s
let bang x s = is 7 "bang" x s


let fizzBuzzChecks n =
    None 
    |> fizz n 
    |> buzz n 
    |> bang n 
    |> Option.defaultValue (string n)
      
let fizzBuzz =
    [1..100] |> List.map fizzBuzzChecks

[<EntryPoint>]
let main argv =
    fizzBuzz |> List.iter System.Console.WriteLine
    System.Console.ReadLine() |> ignore
    0

You can also leave off the x s as follows:

let fizz = is 3 "fizz" 
let buzz = is 5 "buzz" 
let bang = is 7 "bang"