The quadrix is equal to 9,999. The term was coined by André Joyce.[1]

As it is the largest four-digit number in decimal, it has been used in carnahan.c, chan-3.c and pete-6.c.[2]


The 2 parts of the name, “quadr” and “ix”, mean 4 and 9, respectively.


Notation Lower bound Upper bound
Scientific notation \(9.999\times10^3\)
Arrow notation \(99\uparrow2\) \(10\uparrow4\)
Steinhaus-Moser Notation 5[3] 6[3]
Copy notation 9[4]
Chained arrow notation \(99\rightarrow2\) \(10\rightarrow4\)
Taro's multivariable Ackermann function A(3,10) A(3,11)
Pound-Star Notation #*(70)*2 #*(71)*2
PlantStar's Debut Notation [2] [3]
BEAF {99,2} {10,4}
Hyper-E notation 99E2 E4
Bashicu matrix system (0)[99] (0)[100]
Hyperfactorial array notation 7! 8!
Bird's array notation {99,2} {10,4}
Strong array notation s(99,2) s(10,4)
Fast-growing hierarchy \(f_1(f_2(9))\) \(f_2(10)\)
Hardy hierarchy \(H_{\omega^2+\omega}(9)\) \(H_{\omega^2}(10)\)
Slow-growing hierarchy \(g_{\omega^2}(99)\) \(g_{\omega^4}(10)\)


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