-- Example 1
for a = 1, 3 do
    for b = 1, 3 do
        for c = 1, 3 do
            for d = 1, 3 do
                print(a .. b .. c .. d)
            end
        end
    end
end

-- Example 2
local function f(i)
    local str = ""
    for j = 1, 4 do
        local n = math.floor(i/3^(4 - j)%3) + 1
        str = str .. n
    end
    return str
end

for i = 0, 3^4 - 1 do
    print(i, f(i))
end