# 2010 Mathematics Game Update

[Photo by pfala.]

Thanks to John Cook’s article about factorials in the recent Mathematics and Multimedia Carnival, we’re adding new rules to the 2010 Mathematics Game.

Let’s play with multifactorials!

## New Rules

(n!)! = a factorial of a factorial
n!! = a double factorial = the product of all integers from 1 to n that have the same parity (odd or even) as n
n!!! = a triple factorial = the product of all integers from 1 to n that are equal to n mod 3
$n !^k$ = product of all integers from 1 to n that are equal to n mod k, where both n and k must be constructed from the year digits

I did a search this morning and realized that John’s article barely scratched the surface of the topic. I think we need to draw a line somewhere. So we will allow multifactorials (with the above limitation regarding n and k) but not subfactorials, superfactorials, hyperfactorials, alternating factorials, primorials, etc.

This week is hyper-busy, so I won’t have time to explore these new numbers for several days. But I look forward to hearing what you all come up with….

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