145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
Find the sum of all numbers which are equal to the sum of the factorial of their digits.
Note: as 1! = 1 and 2! = 2 are not sums they are not included.
Should be straightforward, though I probably want to precompute the factorial and have that be just an array lookup.
...
Okay, that was NOT straightforward, because rust has a view of
static that I wasn't familiar with at all. It was fine once I
found the lazy_static crate, but I don't like how much unfamiliar
boilerplate there is to using that.