Pi function

In mathematics, at least four different functions are known as the pi or Pi function:

• $\pi (x)\,\!$ (pi function) – the prime-counting function
• $\Pi (x)\,\!$ (Pi function) – the gamma function when offset to coincide with the factorial
• Rectangular function
• $\pi (n)\,\!$ – the Pisano period

You might also be looking for:

• $\prod _{n=1}^{\infty }$ – the Infinite product of a sequence
• Capital pi notation