module _34

let numSumDigitFactorials =
    let digitFactorials =
        [|0..9|]
        |> Array.map common.factorial

    let digitFactorialSum n =
        n
        |> common.numDigits
        |> Seq.map (Array.get digitFactorials)
        |> Seq.sum

    [3..1000000]
    |> List.map (fun n -> (n, digitFactorialSum n))
    |> List.filter (fun n -> fst n = snd n)
    |> List.sumBy fst