Overlapping the pf with the negative integers.......gives u ten.............1s.............ten negative 9s and ten negative 19s...........for the 1st 30 negative numbers...........e starts out 2.7...............2 + 7 = 9.............

e (Euler's Number)

The number e is a famous irrational number, and is one of the most important numbers in mathematics.
The first few digits are:

2.7182818284590452353602874713527 (and more ...)

It is often called Euler's number after Leonhard Euler.
And Euler is spoken like "Oiler"