I have been told that urn is limited to 4096 numbers and i believe this is correct but thought i would ask if anyone else has found this? and if so how did you get around this problem when a larger number is required?
Yes. The documentation for [urn] specifies the 4096 limit, and I verified it a long, long time ago while testing the object and building an alternative.
I use lp.ernie for this sort of thing. From Litter Power. .
If you want to stick to factory objects, you could set up N [urn] objects (where N = ceil(number-of-values-you-want / 4096)), banging an urn at random and then adding n*4096 to the nth urn's output. This is not an absolutely perfect emulation of a larger-than-4096-ball-urn, but might serve your purposes.
If all you're after is random-without-immediate-repeats output (which a lot of people ask for), there are simple ways of doing that.