let isEmpty (sc:IEnumerable<Char>) =
    //Seq.isEmpty (sc)
    sc.Contains('4')

let input =
    Enumerable.Range(1,6)
    |> Seq.map (fun (i) -> (i.ToString(),i))
    |> Seq.map (fun (s,i) -> (s |> Seq.map id,i))

let output =
    input
    |> Seq.map (fun (sc,i) -> (sc, isEmpty(sc), i))
    |> Seq.filter (fun (_,isempty,_) -> not isempty)
    |> Seq.map (fun (sc,_,i) -> (sc,i))

// in linqpad use "F# Program"
input.Dump()
output.Dump()