Heptation or septation refers to the 7th hyperoperation. It is equal to the binary function \(\uparrow\uparrow\uparrow\uparrow\uparrow\) in Knuth's up-arrow notation.[1][2]

"a heptated to b" can be written in array notation as \(\{a,b,5\}\), in chained arrow notation as \(a \rightarrow b \rightarrow 5\) and in Hyper-E notation as E[a]1#1#1#1#b.

Heptational growth rate is equivalent to \(f_6(n)\) in the fast-growing hierarchy.


See also

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