Tethrennon-by-deuteron is equal to E100(#^^#^9)100(#^^#^9)100 in Extended Cascading-E Notation.[1] The term was coined by Sbiis Saibian.

Approximations in other notations

Notation Approximation
Bird's array notation \(\{100,100 [1 [2 \neg 2] 2] 3\}\)
Fast-growing hierarchy \(f_{\varphi(9,0)\times 2}(99)\)
Hardy hierarchy \(H_{\omega^{\varphi(9,0)\times 2}}(100)\)


  1. Saibian, Sbiis. 4.3.3 - Forging Extended Cascading-E Numbers Part I. Retrieved May 6, 2014.
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