fun {Prod A B}
    if A =< B then
        A|{Prod A+1 B}
    else nil
    end
end
fun {Sieve S}
    fun {Filter Xs K}
        case Xs of X|Xr then
            if X mod K \= 0 then
                X|{Filter Xr K}
            else {Filter Xr K}
            end
        else nil
        end
    end
in
    case S
    of H|T then H|{Sieve thread {Filter T H} end}
    else nil
    end
end
fun {NotPrime S S2}
    case S of H|T then
        case S2 of X|Y then
            if X == H then {NotPrime T Y}
            elseif X < H then {NotPrime S Y}
            else H|{NotPrime T S2}
            end
        else nil
        end
    else nil
    end
end