The terrible terrible tethracross 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 (X^^^X)^^(X+1) & 100
Bird's array notation ???
Fast-growing hierarchy \(f_{\varepsilon_{\zeta_0+1}}(100)\)
Hardy hierarchy \(H_{\varepsilon_{\zeta_0+1}}(100)\)
Slow-growing hierarchy ???


  1. Saibian, Sbiis. 4.3.7 Extended Cascading-E Numbers Part IOne to Infinity. Retrieved 2017-03-04.
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