from machine import Pin
from time import sleep
while True:
    for i in range (2,8,2):
        led = Pin(i,Pin.OUT)
        led.on()
        sleep(0.4)
        led.off()
    for i in range (4,1,-2):
        led = Pin(i,Pin.OUT)
        led.on()
        sleep(0.4)
        led.off()