const int numLeds = 4;
const int ledPins[numLeds] = {5,4,3,2,}; 

void allLedsOn()
 {
  for (int i = 0; i < numLeds; i++)
   {
    digitalWrite(ledPins[i], LOW);
  }
}

void allLedsOff() 
{
  for (int i = 0; i < numLeds; i++) 
  {
    digitalWrite(ledPins[i], HIGH);
  }
}

void updateLeds(int value) 
{
  for (int i = 0; i < numLeds; i++) {
    digitalWrite(ledPins[i], (value >> i) & 1);
  }
}

void setup()
 {
  for (int i = 0; i < numLeds; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
  
  allLedsOn();
  
  Serial.begin(9600);
}

void loop()
 {
  static int counter = 0;
  
  updateLeds(counter);
  
  counter++;
  if (counter >= (1 << numLeds)) {
    counter = 0;
  }
  
  delay(500);
}