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'''Hexation''' is the operation of repeated ], just as ] is the operation of repeated ] and is a ]. Like pentation and tetration, it has little real-world applications, and has few applications even in mathematics. It is non-commutative, and therefore has two inverse functions, which might be named the '''hexa-root''' and the '''hexa-logarithm (analogous to the two inverse functions for exponentiation: ] function and ]). Hexation is not ]. '''Hexation''' is the operation of repeated ], just as ] is the operation of repeated ] and is a ]. Like pentation and tetration, it has little real-world applications, and has few applications even in mathematics. It is non-commutative, and therefore has two inverse functions, which might be named the '''hexa-root''' and the '''hexa-logarithm''' (analogous to the two inverse functions for exponentiation: ] function and ]). Hexation is not ].


The word "Hexation" was coined by ] from the roots ] (six) and ]. It is part of his general naming scheme for ]. The word "Hexation" was coined by ] from the roots ] (six) and ]. It is part of his general naming scheme for ].
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*<math> 2 \uarr^{4} 2 = 4</math> *<math> 2 \uarr^{4} 2 = 4</math>

This is the reason why hexation is not normally used in mathematics: the numbers it produces are so vast that they have little use.


{{Hyperoperations}} {{Hyperoperations}}

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Hexation is the operation of repeated pentation, just as pentation is the operation of repeated tetration and is a hyperoperation. Like pentation and tetration, it has little real-world applications, and has few applications even in mathematics. It is non-commutative, and therefore has two inverse functions, which might be named the hexa-root and the hexa-logarithm (analogous to the two inverse functions for exponentiation: nth root function and logarithm). Hexation is not elementary recursive.

The word "Hexation" was coined by Reuben Goodstein from the roots hexa- (six) and iteration. It is part of his general naming scheme for hyperoperations.

Hexation can be written in Knuth's up-arrow notation as a ↑ ↑ ↑ ↑ b {\displaystyle a\uparrow \uparrow \uparrow \uparrow b} or a 4 b {\displaystyle a\uparrow ^{4}b} .

Extension

It is not known how to extend hexation to complex or non-integer values.

Selected values

As its base operation (pentation) has not been extended to non-integer heights, hexation a 4 b {\displaystyle a\uparrow ^{4}b} is currently only defined for integer values of a and b where a > 0 and b ≥ 0. Like all other hyperoperations of order 3 (exponentiation) and higher, pentation has the following trivial cases (identities) which holds for all values of a and b within its domain:

  • 1 4 b = 1 {\displaystyle 1\uparrow ^{4}b=1}
  • a 4 1 = a {\displaystyle a\uparrow ^{4}1=a}

Other than the trivial cases shown above, hexation generates extremely large numbers very quickly such that there is only one fnon-trivial case that produces numbers that can be written in conventional notation, as illustrated below:

  • 2 4 2 = 4 {\displaystyle 2\uparrow ^{4}2=4}

This is the reason why hexation is not normally used in mathematics: the numbers it produces are so vast that they have little use.

Hyperoperations
Primary
Inverse for left argument
Inverse for right argument
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