Counting in bijective base 62 The task is to generate all the strings from 'a' to '999' including upper case characters like so:

'a', 'b', 'c' ... 'y', 'z', 'A', 'B', 'C' ... 'Y', 'Z', '0', '1', 2' ... 
'8', '9', 'aa', 'ab', 'ac' ... 'az', 'aA', 'aB' ... 'aZ', 'a0' ... 'a9', 'ba'


and so on (filling in the gaps), optionally starting with the empty string.

Input:


The amount of consecutive characters the program has to print up to.


Output:


An array containing each string OR one string per line


Clarifications:


The order doesn't matter, you can print uppercase or lowercase letters first if you want.
The output can return any type of enumerable, doesn't have to be an array specifically, although I doubt printing all the combinations won't be the easiest way to go.
An input of 3 would print all the string from 'a' (or '') to '999'‚ an input of 5 up to '99999' and so on.
Jelly, 7 bytes

ØWṖṗR;/


This is a monadic link that accepts an integer as input and returns an array of strings.

Try it online!

How it works

ØWṖṗR;/  Main link. Argument: n

ØW       Yield 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_'.
  Ṗ      Remove the last element (underscore).
    R    Range; yield [1, ..., n].
   ṗ     Cartesian product. For each k in the range, this yields the arrays of all
         strings of alphanumeric characters.
     ;/  Concatenate the arrays of strings of each length.