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Not to be confused with grantethrathoth.

Grand tethrathoth is equal to E100#^#^#...#^#^#100 (tethrathoth #'s) = E100#^^#100#2 in Extended Cascading-E Notation.[1][2] The term was coined by Sbiis Saibian. In Nested Cascading-E Notation, this number is equal to E100#^^#^#100#2. Grand tethrathoth is comparable to Bowers' goppatothplex.

## Etymology

The name of this number is based on the word "grand" and the number "tethrathoth".

## Approximations in other notations

Notation Approximation
BEAF $$X \uparrow\uparrow \text{tethrathoth}\ \&\ 10$$
$$\approx X\uparrow\uparrow(X\uparrow\uparrow X\& 100)\& 100$$[3]
Bird's array notation $$\{100,\text{tethrathoth} [1 \backslash 2] 2\}$$
Hyperfactorial array notation $$(100![1,1,1,1,2])![1,1,1,1,2]$$
Fast-growing hierarchy $$f_{\varepsilon_0}(f_{\varepsilon_0}(100))$$
Hardy hierarchy $$H_{\varepsilon_0 2}(101)$$
Slow-growing hierarchy $$g_{\vartheta(\varepsilon_{\Omega+\vartheta(\varepsilon_{\Omega+1})})}(100)$$

## Sources

1. Saibian, Sbiis. 4.3.5 Cascading-E Numbers. Retrieved 2015-12-23.
2. Sbiis Saibian's Ultimate Large Numbers List - Part III
3. Using notation $$X\uparrow\uparrow(a)\&b=X\uparrow\uparrow c\& b$$, where $$c$$ is the value of the array $$a$$