Fast Factorial Algorithms

A cached map will do best if you actualy need a fast factorial. There are very little entries before the numbers become pointlessly big.

To all commenting about the Sitrling formula, there is a separate page linked at the end for approximations http://www.luschny.de/math/factorial/approx/SimpleCases.html which contains many advanced options to compare for that.

I hoped this would help me solve some more Project Euler [1] problems. Unfortunately, the algorithms given are not explained in detail, so the learning experience is somewhat mediocre. Then again, I have ChatGPT to elucidate them for me.

This article [2] has some interesting details on the swinging factorial function n≀, but I can't seem to find the essay that it references: "Swing, divide and conquer the factorial", 2008.

[1] https://projecteuler.net/

[2] https://oeis.org/A000142/a000142.pdf

No Stirling formula?