primes

primes.fs

let divisors x =
  List.init (int (Math.Sqrt(float x))) (fun x -> x + 1)
  |> List.filter (fun y -> x % y = 0)
  |> List.map (fun y -> [y ; x / y])
  |> List.reduce (fun x y -> x @ y)
  |> List.sort

let isPrime x =
  List.length (divisors x) = 2


let primesBetween x y =
    seq { for num in x..y do
            if (isPrime num)
              then yield num }