Nested Logarithm
In number theory (e.g., Ivić 2003), the symbol log_kx is commonly used to mean the nested logarithm (also called the repeated logarithm or iterated logarithm) [画像:ln...ln_()_(k)x], where lnx is the natural logarithm.
Care must be taken based on context as to when the notation log_kx denotes the logarithm to base k and when it means the k-nested natural logarithm.
The plots above show lnz, lnlnz, and lnlnlnz in the complex plane.
The penchant for formulas and bounds containing a profusion of nested logarithms has led to the following joke. What sound does a drowning analytic number theorist make? A: log log log log... (Havil 2003, p. 115).
See also
Binary Logarithm, Common Logarithm, Logarithm, Natural LogarithmExplore with Wolfram|Alpha
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References
Canadian Mathematical Society. Student Mathematical Communicator. March 2001. http://www.cms.math.ca/Students/en/Newsletter/March2001/cmsletter/node7.html.Havil, J. Gamma: Exploring Euler's Constant. Princeton, NJ: Princeton University Press, 2003.Ivić, A. "On a Problem of Erdős Involving the Largest Prime Factor of n." 5 Nov 2003. http://arxiv.org/abs/math.NT/0311056.Referenced on Wolfram|Alpha
Nested LogarithmCite this as:
Weisstein, Eric W. "Nested Logarithm." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/NestedLogarithm.html