[Jetmech Jr.]

...but it's not coming to me.

http://www.funnyjunk.com/pages/mindreader.htm

EDIT: Figured it out. Yes.

[Rictor]

I saw this a feew years back, figured it out and promptly forgot. And now I can't for the life of me think of what it was.

...so, how does it work?

[Jetmech Jr.]

Spoiler:

If you do the math for, say 99, you'll come up with 81. If you do the math for another number during the same turn, it'll come up with the same symbol. It's all in the math . The symbols on the list do change every turn, though.

[Col. Fishguts]

Spoiler:

You always end up with multiples of 9, and all of the symbols to those numbers are the same.

I've seen a better version once on TV that included words, but it only works in german.