In a manner relating to or involving factorials (the product of a number and all positive whole numbers below it); in terms of factorial mathematics.
From 'factorial' plus '-ly' (adverbial suffix). A specialized mathematical adverb used when discussing factorial operations and their properties.
Factorials explode in size insanely fast—10! is 3.6 million, and 20! is 2.4 quintillion. This explosive growth is why factorials control the mathematics of arrangements and combinations—there are astronomically many ways to arrange things.
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