Code is getting stuck

Questions
1 

function setup()
    --displayMode(FULLSCREEN)
    SCALE = 100
    MAXIMUM = SCALE--100
    
    --parameter.integer("Scale", 3, 100, 20, function(v) SCALE = v end)
    PERCENT = "0%"
    parameter.watch("PERCENT")
    
    tab ={}
    for x = 1, MAXIMUM do
        tab[x] = {}
        for y = 1, MAXIMUM do
            tab[x][y] = 0
        end
    end
    
    for v = 1, MAXIMUM do
        tab[v][1] = 1
        tab[1][v] = 1
    end
    
    local n1 = 0
    for x = 2,MAXIMUM do
        for y = 2,MAXIMUM do
            tab[x][y] = tab[x][y-1] + tab[x-1][y] + tab[x-1][y-1]
            if x == y + 2 then
                --print("1/" .. tab[x][y] .. " equals " .. 1/tab[x][y])
                n1 = n1 + 1/tab[x][y]
            end
        end
    end
    --print("Sum: " .. n1)
    
    --print(isPrime(5), math.ceil(math.sqrt(5)))
    --AMOUNT = 1
end

function draw()
    background(0)
    font("Futura-CondensedMedium")
    --l = 1
    local loading = 0
    for x = 1,SCALE do
        for y = 1,SCALE do
            loading = loading + 1
            --if tab[x][y] < math.maxinteger then -- Why?
            i = math.floor(800/SCALE)
            fill(255, 255, 255, 255)
            if x == y then
                fill(58, 255, 0, 255)
            elseif tab[x][y] == 1 then
                fill(255, 166, 0, 255)
            elseif math.sqrt(tab[x][y]) == math.floor(math.sqrt(tab[x][y])) then
                fill(255, 0, 0, 255)
            --[[elseif tab[x][y]%3 == 0 then
                fill(85, 85, 85, 255)
            elseif tab[x][y]%5 == 0 then
                fill(130, 130, 130, 255)]]
            elseif isPrime(tab[x][y]) then
                fill(0, 83, 255, 255)
            end
            --[[fontSize(i)
            f,_ = textSize(tab[x][y] .. "")
            while f > WIDTH/SCALE do
                i = i - 1
                fontSize(i)
                f,_ = textSize(tab[x][y] .. "")
            end
            text(tab[x][y] .. "", WIDTH*(x-.5)/SCALE, HEIGHT*(y-.5)/SCALE)]]
            rect((x-1)*WIDTH/SCALE, (y-1)*HEIGHT/SCALE, WIDTH/SCALE, HEIGHT/SCALE)
            
            --[[l = l + 1
            if AMOUNT > l then
                AMOUNT = AMOUNT + 1
                break break
            end]]
        
            PERCENT = (100*loading/SCALE^2) .. "%"
            print("Handled " .. loading .. " of " .. SCALE^2 .. " numbers\
" .. PERCENT)
        end
    end
end

function isPrime(n)
    for x = 2, math.ceil(math.sqrt(n)) do
        --print(n, x, n%x)
        if n%x == 0 then
            return false
        end
    end
    return true
end

The last message it prints is:

Handled 1279 of 10000.0 numbers
12.79%

Then it doesn’t print anything, but won’t continue.

2

You’re doing too much in draw. The frames per second is probably 0. You’re calling isPrime a lot which is slowing draw down. You should determine if a number is prime once in setup and not constantly in draw.