void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(9, OUTPUT);
}


// the loop function runs over and over again forever
void loop() {
  delay(50); // milliseconds
  int LED_pin = 13;
  for (int LED_pin = 13; LED_pin >=9; LED_pin--) {
    if (random(0, 4) >= 3) digitalWrite(LED_pin, HIGH); else digitalWrite(LED_pin, LOW);
    //digitalWrite(LED_pin, HIGH);
  }
}