1. Choose a a number made up of ones (up to nine digits).
2. The answer will be a series of consecutive digits beginning
   with 1, up to the number of ones in the given number, and
   back to 1.

   Example:

1. If the number is 11111, (5 digits) -
2. The square of the number is 123454321.
   (Begin with 1, up to 5, then back to 1.)

   See the pattern?

1. If the number is 1111111, (7 digits) -
2. The square of the number is 1234567654321.
   (Begin with 1, up to 7, then back to 1.).

This is an easy one, but it should be good for a quick example of your mental math abilities. Challenge a friend and BEAT THE CALCULATOR!