Today's Free-for-all Friday challenge at the mentalfloss.com Brain Game can be solved with just a single letter of the alphabet. Identify the correct missing letter in the following sequence, and WHY it belongs there. (As the title suggests, the answer is NOT the letter "E.") Good luck!

E, O, E, R, E, X, ?, T, E, N

Here is the SOLUTION.

THE SOLUTION:

The missing letter is N.

The letters represent the final letter in each number from 1 to 10: onE, twO, threE, fouR, fivE, siX, seveN, eighT, ninE, teN.

Thanks for playing, and have a swell weekend. Rest up for Monday Math Square #101!