Ackermann Function

The Ackermann function (named after mathematician Wilhelm Ackermann) is the simplest known example of a well defined total function which is computable, but not Primitive Recursive (calculable using only for loops with a fixed upper limit).

 Ackermann(0, j) = j + 1
 Ackermann(i, 0) = Ackermann(i - 1, 1)                    for i>0
 Ackermann(i, j) = Ackermann(i - 1, Ackermann(i, j - 1))  for i>0 and j>0

See ReallyBigNumbers for some more discussion of Ackermann's function

Interesting... anyone care to give a BigOh value for this function?

Also see


EditText of this page (last edited July 10, 2013) or FindPage with title or text search