Getting Dice All Random

In my first post I mentioned that I had started to get interested in the maths of RPGs from the probabilities in Apocalypse World. There was something else that started me thinking, which is when one of the regulars in the gaming group I play with asked a question on his tabletop role-playing game blog, False Machine.

P was looking at randomly generating an island from a series of entries in a table. He had come up with a means to do that, but only on a computer, which meant while the island was randomly generated the setting would be determined ahead of his session. To him, the problem was, as he put it at the end of the post:

I need a dice method that can randomise 343 hexes

I've always had a strange little fascination with powers of numbers, so this jumped out at me as soon as I saw it. 343 is 7*7*7, which means that you could have seven tables, with seven rows and seven columns; you could then get any entry out of the 343 in your master list by rolling three d8s and re-rolling any 8s.

Problem solved! Until P realised later that there were actually 330 entries in the table for Isle of the Unknown. But this wasn't a problem either, if we imagined the entries arranged in ten tables, each with three columns and 11 rows. Roll a d10 for the table, a d3 (or d6/2 if you must be formal) and a d12 with re-rolls on the 12s. Again, problem solved!

Which got me thinking...

GMs who like to make things up through random tables could possibly have a large number of random encounters or random elements that they would like in tables. 330 or even 343 entries could be quite small. Is there, in general, a sensible schema that we can use for producing sets of random tables for game data, that we can index with dice? Let's assume d4, d6, d8, d10, d12 and d20s are available.

To put some bounds on this, let's assume, for now (although it may be easily extendable, who knows) that we want to consider for sets of random tables with up to 400 elements in total. I'm going to have a think about this and let you know what I think over the next week or so, as well as share a small random table of my own for In A Wicked Age.