int led[] = {3, 5, 6, 9}; //array



void setup() {  
  for (int i=0 ; i <=3 ; i++){
    pinMode(led[i], OUTPUT);
    }   
}

void loop(){            // the loop function runs over and over again forever
  for (int i=0 ; i <=3 ; i++){
  ledBlink(led[i], 500);
 }
}

void ledBlink(int p, int t){   //p is LED pin number; t is time(ms) for blink
  digitalWrite(p, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(t);                      // wait for a second
  digitalWrite(p, LOW);   // turn the LED off by making the voltage LOW
  delay(t);       
}