int ledPins[6];

void setup() {
  for (int i = 0; i < 6; i++) {
    ledPins[i] = i;
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  for (int j = 5; j >= 0; j--) {
    digitalWrite(ledPins[j], HIGH);  
    delay(200);                      
  }

  for (int j = 5; j >= 0; j--) {
    digitalWrite(ledPins[j], LOW);  
    delay(200);         
  }
}