import time
from machine import Pin

led_index_list=[0,4,16,17]
led_pin_list = [Pin(pin, Pin.OUT) for pin in led_index_list]
for pin_led in led_pin_list:
    pin_led.value(0)

while True:
    for pin_led in led_pin_list:
        pin_led.value(not pin_led.value())
        time.sleep(0.05)