Ever since can remember myself, I was (among other weird things) summing numbers on the number plates, e.g.
gives you if you do the following
A weirdness comes after the observation that no matter the order you always get
I found a trick that brought much joy to much childhood – you can always drop a number , which, among many things, means you can drop all combinations
In this case, you can drop first two digits and straight away, then depending on your arithmetics methods you get number at most two-step.
This method comes from one interesting property of numbers and there is a cool dependency between the number of digits in the numbers and a maximum possible combination to squeeze that one last digit that contains information on the original number.
An example. A plate with
containes a number because you drop and .
A long way would be