const int ledPins[] = {4, 11, 13};
const int numPins = sizeof(ledPins) / sizeof(ledPins[0]);  
const int delayTime = 1000;

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

void loop() {
  for (int i = 0; i < numPins; ++i) {
    digitalWrite(ledPins[i], HIGH);
    delay(delayTime);
    digitalWrite(ledPins[i], LOW);
  }
}