Undecation

Undecation refers to the function \(a \uparrow^{9} b\), where Arrow Notation is used.

The n undecated to m is n decated to n decated to ... decated to n (m n's).

Undecation can be written in array notation as \(\lbrace a,b,9 \rbrace\), in chained arrow notation as \(a \rightarrow b \rightarrow 9\) and in Hyper-E notation as \(E(a)\#1\#1\#1\#1\#1\#1\#1\#1\#b\).

Undecational growth rate is equivalent to \(f_9(n)\) in the fast-growing hierarchy.