Just as exponentiation of natural numbers is motivated by repeated multiplication, it is possible to define an operation based on repeated exponentiation; this operation is sometimes called hyper-4 or tetration. Iterating tetration leads to another operation, and so on, a concept named hyperoperation. This sequence of operations is expressed by the Ackermann function and Knuth's up-arrow notation. Just as exponentiation grows faster than multiplication, which is faster-growing than addition, tetration is faster-growing than exponentiation. Evaluated at , the functions addition, multiplication, exponentiation, and tetration yield 6, 9, 27, and () respectively.
Just as exponentiation of natural numbers is motivated by repeated multiplication it is possible to define an operation based on repeated exponentiation; this operation is sometimes called hyper-4 or tetration Iterating tetration leads to another operation and so on a concept named hyperoperation This sequence of operations is expressed by the Ackermann function and Knuth's up-arrow notation Just as exponentiation grows faster than multiplication which is faster-growing than addition tetration is faster-growing than exponentiation Evaluated at  the functions addition multiplication exponentiation and tetration yield 6 9 27 and () respectively