self defined counter function

Hi admins,

I got a conceptual question on creating a stored procedure
I need for my app. First the description of the problem:

I need a counter which works with 36 possible values per
character [0-9 and thereafter A-Z].
That means if incremented it should return values as follows:
0000
0001
0002
...
0009
000A
000B
000C
...
000X
000Y
000Z
0010
0011
0012
...

and so on.

My question is if anybody has already implemented such a
user-defined 'sequence' in PL/PGSql or if anyone has a great
idea on how to do that. The only solution I see at present is
to do that in PHP which is used to code the mentioned userland.

I suggest to solute on doing the following.

- I create a sequence on the DBS
- I get the next value of this sequence
- I convert the next value in PHP in the code I need

The problem I see on doing this is that I always need to
convert if I want to get any kind of information about the
counter. For example it could be that I only want to know
what the last given value was. Because of the high traffic
value on the application I have to take care of, that the
information I read is quite correct at any time. So if I
have to convert the value of the sequence therefore I need
a little time. In the meantime the value could have changed
and my information is worthless.

I think the best way would be to code a store procedure
for the problem. Any ideas would be welcome.

Enrico Ortmann