int led [4]={(10,11,12,13)};
 void setup() { 
  pinMode(led, OUTPUT); 
  } 
  void loop() {
  int n; 
  for (n=0;n<6;n++) {
   digitalWrite(led [n], HIGH); 
   delay(150); 
   digitalWrite(led [n], LOW); 
   } 
   for (n=6;n>0;n--) { 
   digitalWrite(led [n], HIGH); 
   delay(150); 
   digitalWrite(led [n], LOW);
    }
  }