Difference between revisions of "Knuth's up-arrow notation"

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(Definition)
(Definition)
 
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\(a \uparrow b=a^b\)
 
\(a \uparrow b=a^b\)
  
\(a \uparrow\uparrow b=\underbrace{a^{a^{{\cdots}^a}}}_{b}\)
+
\(a \uparrow\uparrow b=\underbrace{a^{a^{.^{.^{.^{a}}}}}}_{\text{b a's}}\)
  
\(a \uparrow\uparrow\uparrow b=\underbrace{a \uparrow\uparrow a \uparrow\uparrow a\cdots\uparrow\uparrow a}_{b}\)
+
\(a \uparrow\uparrow\uparrow b=\underbrace{a \uparrow\uparrow a \uparrow\uparrow a\cdots\uparrow\uparrow a}_{\text{b a's}}\)
  
\(a \uparrow^{n+1} b=\underbrace{a \uparrow^n a \uparrow^n a\cdots a\uparrow^n a}_{b}\)
+
\(a \uparrow^{n+1} b=\underbrace{a \uparrow^n a \uparrow^n a\cdots a\uparrow^n a}_{\text{b a's}}\)
  
This notation is supposed to be evaluated from the right if there is more than one patch of arrows and there are no brackets.  
+
This notation is supposed to be evaluated from the right if there is more than one patch of arrows and there are no brackets.
  
 
== Examples ==
 
== Examples ==
 
\(3\uparrow\uparrow\uparrow3=3\uparrow\uparrow3\uparrow\uparrow3=3\uparrow\uparrow3\uparrow3\uparrow3=3\uparrow\uparrow3\uparrow27=3\uparrow\uparrow7625597484987=\)a power tower that will reach all the way to the Sun
 
\(3\uparrow\uparrow\uparrow3=3\uparrow\uparrow3\uparrow\uparrow3=3\uparrow\uparrow3\uparrow3\uparrow3=3\uparrow\uparrow3\uparrow27=3\uparrow\uparrow7625597484987=\)a power tower that will reach all the way to the Sun

Latest revision as of 16:55, 12 February 2017

Knuth's up-arrow notation is a notation for expressing large numbers. However, there are some numbers so large that even this up-arrow notation is not enough.

Definition

\(a \uparrow b=a^b\)

\(a \uparrow\uparrow b=\underbrace{a^{a^{.^{.^{.^{a}}}}}}_{\text{b a's}}\)

\(a \uparrow\uparrow\uparrow b=\underbrace{a \uparrow\uparrow a \uparrow\uparrow a\cdots\uparrow\uparrow a}_{\text{b a's}}\)

\(a \uparrow^{n+1} b=\underbrace{a \uparrow^n a \uparrow^n a\cdots a\uparrow^n a}_{\text{b a's}}\)

This notation is supposed to be evaluated from the right if there is more than one patch of arrows and there are no brackets.

Examples

\(3\uparrow\uparrow\uparrow3=3\uparrow\uparrow3\uparrow\uparrow3=3\uparrow\uparrow3\uparrow3\uparrow3=3\uparrow\uparrow3\uparrow27=3\uparrow\uparrow7625597484987=\)a power tower that will reach all the way to the Sun