[1 .. 5000] |> Seq.filter (fun n -> n == n.ToString() |> List.toArray |> (fun s -> float(s - '0')) |> List.sumBy (fun x -> System.Math.Pow x)) |> Seq.iter (printfn "%A") // System.Linq.Enumerable.Range(1,5000).Where(n => n == n.ToString().Sum(x => Math.Pow(toInt(x), toInt(x)))) //|t when t < 50 -> ...