An inherently iterative computation of ackermann's function

AbstractThe Ackermann function is defined recursively by A(0,n)=n + 1; A(i,0) = A(i - 1, 1) for i>0; and A(i,n)=A(in −1, A(i-1))for i,n > 0. An iterative algorithm for computing A(i,n) is presented. It has O(i) space complexity and O(iA(i,n)) time complexity, both of which are much smaller than the corresponding quantities for an algorithm based directly on the recursive definition