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Vigintation refers to the 20th hyperoperation starting from addition. It is equal to $$a \uparrow^{18} b$$, using Knuth's up-arrow notation.[1]

Vigintation can be written in array notation as $$\{a,b,18\}$$, in chained arrow notation as $$a \rightarrow b \rightarrow 18$$ and in Hyper-E notation as E(a)1#1#1#1...1#1#1#b (17 ones).

Vigintational growth rate is equivalent to $$f_{19}(n)$$ in the fast-growing hierarchy.