K-based. A number in Base k, a number is in Base K if all his digits
are from 0 to K-1 (10-Based numbers are numbers used by people). The
value is obtained as this:
an*k**n + ... a0*k**0, where an through a0 are the digits from left
to right order and k** is the power operation.
Though is basic for you to know this concepts :)

> K-based. A number in Base k, a number is in Base K if all his
digits
> are from 0 to K-1 (10-Based numbers are numbers used by people).
The
> value is obtained as this:
> an*k**n + ... a0*k**0, where an through a0 are the digits from left
> to right order and k** is the power operation.
> Though is basic for you to know this concepts :)
Hello Miguel Angel. Help me please. I think that for n=5 with every
base there are 8 invalid numbers, aren't they. and for n=12 invalid
numbers=1815

Unfortunately isn't right. A hint:
Let n the amount of digits, and k the base
for 1 digit you have from 1 to k valid numbers.
for 2 digits you have from 1 to k and from 0 to k, so (k-1)k.
You may do first "Binary Lexicographic Sequence" problem to have a
notion of this :)