.
I just saw several (more than one) posts in this forum asking about last four digits of the numbers of the form .
Probably, it is good time to shed more light on this subject.
Let N be an ARBITRARY fixed natural number (positive integer), and m be another fixed positive integer number.
Consider infinite sequence , n = 1, 2, 3, 4, . . .
Then starting from some , the "m" last digits of the numbers will repeat cyclically.
This statement seems to be very advanced, but its proof is in couple of lines.
For the sequence , the sequence of its "m last digits" is the sequence mod .
There is only finite number of different m-digit numbers, so it will happen INEVITABLY mod = mod for
some n > k for the first time (the Dirichlet's principle, or so name "pigeons principle").
Then after that this equality will repeat periodically/cyclically.