What does MATLAB call the on-board LED Arduino pin 13?

My project is a balancing robot on the MakeBlock Ultimate 2.0 build. The board is an Arduino Mega 2560 clone. I have done it the Arduino way and poorly chosen the tuning values. Now it is time to explore the forth generation software MATLAB. I will start with Blink. The onboard LED is on Arduino pin 13. But MATLAB does not name it that way.

So my question is what does MATLAB call the Arduino 2560 LED pin?

MATLAB says

>> a

a = 

  arduino with properties:

                  Port: 'COM6'
                 Board: 'Mega2560'
         AvailablePins: {'D2-D53', 'A0-A15'}
  AvailableDigitalPins: {'D2-D53', 'A0-A15'}
      AvailablePWMPins: {'D2-D13', 'D44-D46'}
   AvailableAnalogPins: {'A0-A15'}
    AvailableI2CBusIDs: [0]
             Libraries: {'I2C'}

>> writeDigitalPin(a,'13',1)
Invalid pin number. Valid pin numbers for this board Mega2560 are "D2-D53", "A0-A15".
 
>>

(deleted)

  AvailableDigitalPins: {'D2-D53', 'A0-A15'}

Does '13' look like any of these?