The post begins:
So, you know those cars with that keyless entry pad? The one under the driver’s side handle?
And ends with:
I am going to give you a sequence of minimal length that, when you enter it into a car’s numeric keypad, is guaranteed to unlock the doors of said car. It is exactly 3129 keypresses long, which should take you around 20 minutes to go through.
In other words, if you press the sequence of 3,129 numbers he presents, you will get yourself into any car with a keyless entry system.