void setup() {
  // put your setup code here, to run once:
  pinMode(4,OUTPUT);
  pinMode(5,OUTPUT);
  pinMode(6,OUTPUT);
  pinMode(7,OUTPUT);
  pinMode(8,OUTPUT);
  pinMode(9,OUTPUT);
  pinMode(10,OUTPUT);
  pinMode(11,OUTPUT);
  pinMode(12,OUTPUT);
  pinMode(13,OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  for(int i = 4; i < 14; i++){   // this will loop from led 4 to led 13
    digitalWrite(i, HIGH);
    delay(150);
    digitalWrite(i, LOW);
    delay(150);
  }

    for(int i = 13; i > 4; i--){   // this will loop from led 13 to led 4
    digitalWrite(i, HIGH);
    delay(150);
    digitalWrite(i, LOW);
    delay(150);
  }

}