OMG!!! LOL!!! It turns out that if we calculate 1/n! for every number starting from 0, then add up all the terms, the answer is e.
Euler’s identity is the “To be or not to be” of mathematics, the most famous line in the oeuvre and a piece of cultural heritage that resonates beyond its field: e^iπ + 1 = 0
...The equation is mind-blowing. It cleanly unites the five most important numbers in math: 1, the first counting number; 0, the abstraction of nothing; π, the ratio of a circle’s circumference to its diameter; e, the exponential constant; and i, the square root of minus one.