Math can be colorful, right?
Math game based on changing color patterns. Add, subtract, or multiply yourself to the number one spot. There's a time limit, but that can always be extended with the help of Tapjoy.
Paid version versus free uses higher numbers making it possible to get higher numbers quicker. Also, paid version gets more bonus points from offerwall.
Openfeint integration with many achievements possible!
P.S. Don't forget your order of operations!