module _47

let consequtivePrimes =
    let max = 200000
    let count = 4
    let d = common.divisors max
    let p = common.primeArray ((int)(max/2)) |> Set.ofArray

    d
    |> Seq.mapi (fun i ds -> 
        let ds = i::ds |> Set.ofList
        let dp = Set.intersect ds p
        (i, Set.count dp))
    |> Seq.filter (snd >> (=) count)
    |> Seq.map fst
    |> Seq.windowed count
    |> Seq.find (fun ns -> ns.[count - 1] - ns.[0] = count - 1)