Pentadecation refers to the 15th hyperoperation starting from addition. It is equal to \(a \uparrow^{13} b\) in Knuth's up-arrow notation.

Pentadecation can be written in array notation as \(\{a,b,13\}\) and in chained arrow notation as \(a \rightarrow b \rightarrow 13\).

Pentadecational growth rate is equivalent to \(f_14(n)\) in the fast-growing hierarchy.

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