Mini-challenge - accurate factorials

[John Keith]

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Mild spoilers...
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[url=https://oeis.org/A034886]A034886[/url]- Number of digits in n!.

[url=https://oeis.org/A004154]A004154[/url]- Omit trailing zeros from factorial numbers.

There are formulas to compute these values but for the small numbers we are concerned with it is easier to just look them up. :)

As an aside, the HP 49 and 50 in Exact mode will give the exact value for n! limited only by the number of digits that will fit in memory. For the 49G+ and 50, the program FFAC is substantially faster than the built-in factorial function. On my HP 50, 1000! (2568 digits) takes about 29 seconds, whereas 1000 FFAC takes about 380 milliseconds.