In 1730, Leonhard was appointed professor of physics, and three years later he became the professor of mathematics. Leonhard joined the Berlin Academy of Science in 1741. Later in 1744, he became director of the academy's mathematics section. He produced just more written work on mathematics than anyone else. It was once said that he could write a new paper in about thirty minutes and his desk was always covered with his pending works.
S stands for summation.
Leonhard Euler was the first to prove that e is an irrational number. He was also the first to consider sin, cos, and tan as abbreviations for sine, cosine, and tangent. Euler found the solution to a problem that many top mathematicians could not figure out. This was called the Basel problem. Here the sum is divided by all natural numbers n, while the product is divided by all prime numbers.