const int LEDs[]={0,5,9,13};
const int NumLEDs=sizeof(LEDs)/sizeof(LEDs[0]);
void setup()
{
  for (int i=0;i<NumLEDs;i++)
  {
    pinMode(LEDs[i],OUTPUT);
  }
}

void loop()
{
  for (int i=0;i<NumLEDs;i++)
  {
    digitalWrite(LEDs[i],HIGH);
    delay(500);
    digitalWrite(LEDs[i],LOW);
  }
}