For 10 points, name this mathematician who determined no route existed that crossed each of the Seven Bridges of Konigsberg exactly once.
When a function named after this man is applied to a prime p to a power k, it returns quantity [p to the k] minus quantity [p to the k minus one]. In addition to that function that counts the integers less than n that are coprime to n, this man names a first-order numerical process used to solve ordinary (*) differential equations. This namesake of a totient function names a value that is the limit of the quantity one plus one over n, all to the n. This man's namesake number is the base of the natural logarithm. For 10 points, name this mathematician who determined no route existed that crossed each of the Seven Bridges of Konigsberg exactly once.
When a function named after this man is applied to a prime p to a power k, it returns quantity [p to the k] minus quantity [p to the k minus one].
Leonhard Euler (pronounced “Oiler”; in order the described things are Euler’s totient function, Euler’s method, and Euler’s number)