int leds[] = {8,9,10,11,12,13};
void setup() {

      for (int i = 0; i <= 5; i++) {
        pinMode(leds[i], OUTPUT);   // initialise all the LEDs in a loop one at a time
      }

}

void loop() {	            // the loop function runs over and over again forever

      for (int i = 0; i <= 5; i++) {
        digitalWrite(leds[i], HIGH);    //turn on each LED one at a time
        delay(200);
        digitalWrite(leds[i], LOW);     //turn off each LED one at a time
        delay(200);
      }
}