FizzBuzz from http://fsharpforfunandprofit.com/posts/convenience-active-patterns/

FizzBuzz2.fs

// setup the active patterns
let (|MultOf3|_|) i = if i % 3 = 0 then Some MultOf3 else None
let (|MultOf5|_|) i = if i % 5 = 0 then Some MultOf5 else None

// the main function
let fizzBuzz i = 
  match i with
  | MultOf3 & MultOf5 -> printf "FizzBuzz, " 
  | MultOf3 -> printf "Fizz, " 
  | MultOf5 -> printf "Buzz, " 
  | _ -> printf "%i, " i
  
// test
[1..20] |> List.iter fizzBuzz