int leds[] = {2, 4, 5};
int count = 3;

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

void loop() {
  for (int i = 0; i < count; i++) {
    digitalWrite(leds[i], HIGH);
    delay(200);
    digitalWrite(leds[i], LOW);
  }
}