For 10 points, name this eighteenth-century Swiss mathematician who names the number e.
This mathematician introduced a function that, for a prime p to the power k gives "p to the k-minus-one times the quantity p minus one." He introduced notation like "sigma" for sums, "sin," "cos," "tan," and "f of x." He introduced a function that returns the number of integers less than or equal to n that are coprime to it, his (*) totient function, "phi." He identified the fact that "e to the i-pi equals negative one." He founded graph theory by solving the Seven Bridges of Königsburg problem. For 10 points, name this eighteenth-century Swiss mathematician who names the number e.
This mathematician introduced a function that, for a prime p to the power k gives "p to the k-minus-one times the quantity p minus one."
Leonhard Euler ["oiler"]