int pattern[4] = {3,5,6,9};
int x;

void setup() {
 for (x=0; x<4; x++){
  pinMode(pattern[x], OUTPUT);
 }

}

void loop() {
  // x++ and X=x+1 are same;
  for (x=0; x<4; x=x+1){
    digitalWrite(pattern[x], HIGH);
    delay(1000);
    digitalWrite(pattern[x], LOW);
    delay(1000);
  }

}