Category:Ackermann function

The Ackermann function or Ackermann-Péter function is defined recursively for non-negative integers m and n as follows:

0 \mbox{ and } n = 0 \\ A(m-1, A(m, n-1)) & \mbox{if } m > 0 \mbox{ and } n > 0. \end{cases}"/>

In the theory of computation, the Ackermann function is a simple example of a recursive function that is not primitively recursive. Note that this function grows very quickly -- even A(4, 3) cannot be feasibly computed on ordinary computers.

Category: Introductory examples