from machine import Pin
from time import sleep
led_21 = Pin(21, Pin.OUT)
led_19 = Pin(19, Pin.OUT)
led_18 = Pin(18, Pin.OUT)
led_5 = Pin(5, Pin.OUT)
def binarycount(x):
    binary = '{0:04b}'.format(x)
    led_21.value(int(binary[0]))
    led_19.value(int(binary[1]))
    led_18.value(int(binary[2]))
    led_5.value(int(binary[3]))
while True:
    for j in range (0,4):
        s = (2**j)
        binarycount(s)
        sleep(1)