const int ledPins[] = {13,9,4,1}; 
void setup() 
{
  for (int i = 0; i < 4; i++) 
  {
    pinMode(ledPins[i], OUTPUT);
  }
}
void loop()
{
  for (int num = 0; num <= 15; num++) 
  {
    displayBinary(num); 
    delay(1000);
    displayBinary(~num & 0x0F); 
    delay(1000);
  }
  delay(2000);
}
void displayBinary(int num) 
{
  for (int i = 0; i < 4; i++) 
  {
    digitalWrite(ledPins[i], (num >> i) & 1);
  }
}