What's that equation that spells a math word?

Question

I can't remember what it was, but I vaguely remember a semi-famous equation that when graphed spells a math word like "equation" or a number, does anyone know what that is?

Answer 1

I believe you may be looking for Tupper's self-referential formula :

$$ \frac{1}{2} < \left\lfloor\text{mod}\left( \left\lfloor \frac{y}{17} \right\rfloor 2^{-17\lfloor x\rfloor - \text{mod}(\lfloor y\rfloor, 17)} , 2\right)\right\rfloor$$

This formula plots any bitmap of 105 by 16 in the range $0 \le x \le 16$ and $k\le y\le k+16$, indexed by $k$.

For a particular 543-digit number, it plots itself (upside down), but there exists a $k$ such as it plots equation, number or anything else you'd want to see.