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The googolgoogoltriplex or googolstackstackstack[1] is equal to $$10 \uparrow\uparrow 10 \uparrow\uparrow 10 \uparrow\uparrow (10^{100})$$. or  $$10 \uparrow\uparrow \text{googolduduex}$$[2]

Aarex Tiaokhiao calls this number googoltreduex.[3]

Username5243 calls this number googoltriduex, and it's equal to 10[2]googolduduex in Username5243's Array Notation.[4]

## Etymology

The name "googolstackstackstack" can be separated into 4 parts, "googol" and 3 "-stack"s, where "n-stack" means $$10\uparrow\uparrow n$$, so 3 "-stack"s means the operation applying 3 times.

## Approximations in other notations

Notation Approximation
Up-arrow notation $$10 \uparrow\uparrow 10 \uparrow\uparrow 10 \uparrow\uparrow(10 \uparrow 100)$$ (exact)
Chained arrow notation $$10 \rightarrow (10 \rightarrow (10 \rightarrow 10^{100} \rightarrow 2) \rightarrow 2) \rightarrow 2$$ (exact)
BEAF $$\{10,\{10,\{10,\{10,100\},2\},2\},2\}$$ (exact)
Hyper-E notation $$\textrm{E}100\#1\#4$$
Hyperfactorial array notation $$(((70!)!1)!1)!1$$
Fast-growing hierarchy $$f_3(f_3(f_3(f_2(324))))$$
Hardy hierarchy $$H_{\omega^33+\omega^2}(324)$$
Slow-growing hierarchy $$g_{\varepsilon_{\varepsilon_{\varepsilon_{\omega^\omega}}}}(100)$$

## Sources

Googol plex bang stack numbers