from machine import Pin
from time import sleep

leds = [Pin(2, Pin.OUT),Pin(4, Pin.OUT), Pin(16, Pin.OUT, Pin(15, Pin.OUT))]
i = 0

while True:
    leds[i].value(not leds[i].value())
    sleep(1)
    if i < len (leds)-1:
        i+=1
    else:
        i = 0