RE: "Reference #"

>Then pseudorandom is fine.  

Pseudorandom does NOT mean unique.  It means unpredictable (within
mathematically provable limits.)  No matter how large the number (even 31
digits), the algorithm can easily produce a sequence like 1, 4509876, 1.  It
may not repeat a number as quickly as that, but it WILL repeat a number (not
the sequence of numbers) sooner than a sequential 31 digit number will.  The
math to prove that is somewhat above my head, but then a lot of things are.

An example might work better.  We have a 1 digit number (0-9).  The
algorithm emits a number: 2.  The next number does not come from a universe
of 0,1,3,4,5,6,7,8,9 but from the exact same universe of 0-9.  The algorithm
might emit a 2, or it might not; you can't predict.
  --buck