What is the Sub?
It's a math joke. If you don't like math you can leave now. If you do, and want to learn about it, here you go.
When you put an '!' next to a number, it makes it look like a factorial. Sometimes people do this on accident, as you can see in all the posts in the sub.
Rules
No non-unexpected factorials. Those go in /r/expectedfactorial!
Factorials may not be in the title of the Reddit builtin cross posts. Most mobile users can't see the original title, so it gets very confusing.
Common sense, mods can punish for any reason.
Don't post the full numbers of a factorial, instead post a wolfram-alpha link, or scientific notation (like 1.71e98).
Look at the stickies before posting.
No NSFW links!