let loopMulTable (n : int) : string =
    let mutable s = "    1   2   3   4   5   6   7   8   9   10\n\n"
    let mutable space = ""
    for i = 1 to n do
        if i > 9 then space <- "  " else space <- "   "
        s <- s + string(i) + space
        for j = 1 to 10 do
            if (i*j) > 9 then space <- "  " else space <- "   "
            s <- s + string(i*j) + space
        s <- s + "\n\n"
    s