int ledPins[] = {23, 22, 19, 18, 17, 16};
void setup() {
  for (int i = 0; i < 6; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  for (int i = 0; i < 6; i++) {
    digitalWrite(ledPins[i], HIGH);
    delay(2000);
    digitalWrite(ledPins[i], LOW);
  }
}