From Linguist on RPI's Lily conferencing system:

* Take your original number (n), subtract 25, tack on 2 zeroes.
* Square ABS (50-n), add that. Voila.  (of course, you don't NEED to
* ABS the 50-n if you're going to square it, but...)  Also, if [ABS
* (50-n)]^2 > 25, you can figure it out with the same method before
* adding to the [n-25]*100.  So... for n>25, n^2=[(n-25)*100] +
* [50-n]^2.  Sounds complicated, but it's not.  Example: square 93.
* That's 68 more than 25, so 6800 + 43^2. 43^2, that's 18 more than
* 25, so 1800 + 7^2, or 1849. Add to 6800, that's 8649.