Just to pile on:
It is quite straightforward to write a program to literally roll a d6, then reroll on a 1-2. In Python, for example, you can do it very few lines
In [1]: d = randint(1,7,1e6) # 7 here because Python is quirky and doesn't include the top number
In [2]: d2 = randint(1,7,1e6)
In...