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J-F Garnier · (This post was last modified: 07-09-2023 08:29 AM by J-F Garnier.)

(07-08-2023 06:55 PM)DA74254 Wrote: WP43 can do 40!
Which displays 815915283247897734345611269596115894272e9

(07-09-2023 06:02 AM)EdS2 Wrote: Yes, that's what I was getting at - whether or not we choose to do SHOW changes the conditions a bit of course.

Similarly, it looks like Free42 can give us 36! - all the significant digits show up in SHOW mode, whereas 37! is too big and misses a few.

Yes, 36! is exact in Free42, but surprisingly 40! =
8.159152832478977343456112695961164e47
has 5 ULP error.
That's a lot for just 4 additional multiplications, unless Free42 doesn't use guard digits in the factorial code, which I can't believe.

Edit: even more weird (on Free42):
39! = 2.039788208119744335864028173990290e46 (correct)
39! * 40 = 8.159152832478977343456112695961160e47 (just 1 ULP error, that's normal here).
So what is going on with the direct 40! calculation ?

J-F