Tethrathoth-by-hyperion is equal to E100#^^#*#100 using Extended Cascading-E Notation.[1] The term was coined by Sbiis Saibian. This number belongs to the Tethrathoth regiment.

Approximations in other notations

Notation Approximation
BEAF \(\{100,100 (X \uparrow\uparrow X) 100\}\)[2]
Bird's array notation \(\{100,100 [1 \backslash 2] 100\}\)
Hyperfactorial array notation \(100![1,99,1,1,2]\)
Fast-growing hierarchy \(f_{\varepsilon_0 {99}}(100)\)
\(\approx \(f_{\varepsilon_0 {\omega}}(100)\)
Hardy hierarchy \(H_{\varepsilon_0^{99}}(101)\)
\(\approx \(H_{\varepsilon_0 {\omega}}(100)\)
Slow-growing hierarchy \(g_{\vartheta(\varepsilon_{\Omega2}{98}+\varepsilon_{\Omega+1})}(100)\)


  1. Saibian, Sbiis. 4.3.7 Extended Cascading-E Numbers Part IOne to Infinity. Retrieved 2017-01-02.
  2. Using particular notation \(\{a,b (X \uparrow\uparrow X) c \#\}\) for \(\{X \uparrow\uparrow b\ \&\ a (X \uparrow\uparrow X) c-1 \#\}\)
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