int timer = 500;
int ledPins[8] = { 1, 2, 3, 4, 5, 6, 7, 8 };
int i;

void setup() {

  for (i = 0; i < 5; i++) {

    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {

  for (i = 0; i < 8; i++) {

    digitalWrite(ledPins[i], HIGH);
    digitalWrite(ledPins[i+1], HIGH);
    delay(timer);
    digitalWrite(ledPins[i], LOW);
  }


  for (i = 6; i >= 0; i--) {

    digitalWrite(ledPins[i], HIGH);
    delay(timer);
    digitalWrite(ledPins[i], LOW);
  }
}