local function factorize( n )
    if n == 1 then return {1} end

    local k, res = 2, {}
    while n > 1 do
        while n % k == 0 do
            res[#res+1] = k
            n = n / k
        end
        k = k + 1
    end
    return res
end

for i = 1, 22 do
    print( string.format( "%2d", i ) .. ":  " .. table.concat( factorize( i ), " * " ) )
end