## FANDOM

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The first few $$a_n$$ for $$n = 0, 1, 2, 3, \ldots$$ are 1, 1, 2, 9, 262144, ... (OEIS A049384). The next number, 5262144, has 183231 digits and starts with 620606987866087447074832055728467... Exponential factorial of 6 is approximately $$10^{4.829261036 \cdot 10^{183230}}$$ and starts with 110356022591769663217914533447534.... The sum of the reciprocals of these numbers is 2.6111149258...

The exponential factorial satisfies the bound $$a_n \leq {^{n-1}n}$$ (テトレーション).

In 超階乗配列表記, expofactorial is equal to n!1.