[seed-prelaunch-2026] Fermat margin note

Sketch

For $n > 2$, consider $x^n + y^n = z^n$.

$$\sum_{i=1}^{n} i = \frac{n(n+1)}{2}$$

1. Reduce to coprime triples.
2. Apply infinite descent.

I have a truly marvelous proof of this theorem, which this margin is too narrow to contain.