anchor.diff:      let isPrime n =
           if n % 2 = 0 then false
           else
  -            let root = int (ceil (sqrt (float n)))
  +            let root = int (sqrt (float n))
               seq {3..2..root} |> Seq.forall (fun i -> n % i <> 0)
   
       let prime =
  
positive.code:     let isPrime (n : int) =
          if n % 2 = 0 then false
          else
              let root = int (ceil (sqrt (float n)))
              seq {3..2..root} |> Seq.forall (fun i -> n % i <> 0)
  
      let num = 600851475143L
      let root = int (ceil (sqrt (float num)))
      let largest =
          seq {2..root}
          |> Seq.filter (fun i -> num % (int64 i) = 0L)
  
negative.code:         nums
          |> Seq.map (fun c -> int64 (string c))
          |> Seq.windowed 13
          |> Seq.map(fun window -> window |> Seq.fold (*) 1L)
          |> Seq.max
  
      printfn "Problem 8: %A" largest
  