Tethracuborfact (also called hecato-tethracubor) is equal to E100(#^^###)^#100 using Extended Cascading-E Notation.[1] The term was coined by Sbiis Saibian.

Approximations in other notations

Notation Approximation
BEAF \(\{100,101(X \uparrow\uparrow\uparrow\uparrow X*X) 2\}\)[2] (weak bound)
Bird's array notation {100,101[1[1\1\2]1\1\2]2}
Strong array notation s(100,101{1{1`1`1`2}1`1`1`2}2)
Fast-growing hierarchy \(f_{{\varphi(3,0)}^{\omega}}(100)\)
Hardy hierarchy \(H_{\varphi(3,0)^{\varphi(3,0)^{\omega}}}(100)\)
Slow-growing hierarchy ???


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