The inverse Ackermann function \(\alpha(N)\) is defined as the least \(n\) such that \(A(n) \geq N\) (the single argument Ackermann function). It is notable on its own for its use in computational complexity theory; there are algorithms known to have time complexity \(O(\alpha(n))\) (or otherwise involving the function). \(\alpha\) is so slow-growing that such algorithms practically run in constant time. This article is a . You can help My English Wiki by expanding it.