Trick 36 : Squaring numbers made up of 1's

Squaring numbers made up of 1's
Choose a a number made up of ones (up to nine digits).

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:

If the number is 11111, (5 digits) -

The square of the number is 123454321.
(Begin with 1, up to 5, then back to 1.)



See the pattern?

If the number is 1111111, (7 digits) -

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!