Googology Wiki
Googology Wiki

Tethra-ogdon is equal to E100#^^#^#8 = E100#^^########100 in Extended Cascading-E Notation.[1] The term was coined by Sbiis Saibian.


The name of this number is based on the number tethrathoth and the root "yotton" from "polyyotton". Polyyotton is the name for a 9-dimensional figure and 9-D figures are constructed from multiple 8-D figures (hence the "poly"), so a "yotton" can be considered a 8-dimensional figure.

Approximations in other notations

Notation Approximation
BEAF \(X \uparrow\uparrow X^8 \&\ 100\)
Bird's array notation \(\{100,9 [1 [2 \neg 2] 2] 2\}\)
Hyperfactorial array notation \(100![1] w/11\)
Fast-growing hierarchy \(f_{\varphi(8,0)}(99)\)
Hardy hierarchy \(H_{\varphi(8,0)}(100)\)
Slow-growing hierarchy \(g_{\vartheta(\varphi(8,\Omega+1))}(100)\)


  1. Saibian, Sbiis. 4.3.3 - Forging Extended Cascading-E Numbers Part I. Retrieved May 5, 2014.