an odd number and the two integers surrounding it's square/2 will always make a pythagorean triple eg. 3/4/5, 5/12/13, 7/24/25, 9/40/41
there was also one i noticed for something in calc two that related to integrals and square roots, but i would have to dig out my notes. it has something to do with the power of the numerator under the root being less than the root causing the integral to be the denominator of the root with the constant flipped to it's negative