#define NUM_LEDS 7
#define DELAY_TIME 4000 
int ledPins[NUM_LEDS] = {2, 4, 6}; 

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

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