Persisting between program runs
This is all very well, but Memoize uses an in memory cache. Jolly's problem is that each time he runs his code his program has to re-do all the work up until the point that it crashes. Using memoize like above won't speed up his code at all as every time the script runs it starts with a fresh empty cache.

What we need to do is what the Wise Old Elf suggested - persist our results between program runs.

Well, Memoize can do that: