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Knuth's Arrows

Tool to write with Arrowed notation of iterative exponentiation by Knuth : a mathematical notation with arrows aiming to write huge integer numbers with repeated powers.

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Knuth's Arrows -

Tag(s) : Arithmetics, Notation System

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# Knuth's Arrows

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## Calculation with Knuth's up-arrows notation A↑↑B

Tool to write with Arrowed notation of iterative exponentiation by Knuth : a mathematical notation with arrows aiming to write huge integer numbers with repeated powers.

## Answers to Questions

### How to calculate using Knuth up-arrows notation?

The Knuth arrows are a repeated exponentiation representation (Knuth up arrows). As multiplication is the repetition of additions ( $$2 \times 3 = 2+2+2$$ ), as exponentiation is the repetition of multiplications (\ = 2 \times 2 \times 2 \)), the knuth arrows is the repetition of exponentiations (also called iterated exponentiation).

Knuth's notation with a single arrow represents a simple power operation

Example: $$3 \uparrow 3 = 3^3 = 27$$

Knuth's notation with 2 arrows is an iterated power

$$a \uparrow \uparrow b = \underbrace{a_{}^{a^{{}^{.\,^{.\,^{.\,^a}}}}}}_{ b\mbox{ times}}$$

Example: $$3 \uparrow\uparrow 2 = 3^3 = 27$$

Example: $$3 \uparrow\uparrow 3 = 3^{3^3} = 3^{27} = 7625597484987$$

Example: $$3 \uparrow\uparrow 4 = 3^{3^{3^3}} = 3^{3^{27}} = 3^{7625597484987}$$

It may be noted that

$$a \uparrow\uparrow b = \underbrace{a_{}\uparrow a\uparrow\dots\uparrow a}_{ b\mbox{ times}}$$

Example: $$3 \uparrow\uparrow 2 = 3 \uparrow 3$$

Example: $$3 \uparrow\uparrow 3 = 3 \uparrow 3 \uparrow 3$$

Knuth's arrows produce immensely large numbers (bingintegers) that dCode can not display without risking blocking your browser, so there's a limit of 100,000 digits.

### What does 3 Knuth up-arrows means?

the 3 arrows (triple arrow) notation is the continuity of the 2 arrows notation (double arrow)

$$a \uparrow\uparrow\uparrow b = \underbrace{a_{}\uparrow\uparrow a\uparrow\uparrow\dots\uparrow\uparrow a}_{ b\mbox{ times}}$$

Example: $$3 \uparrow\uparrow\uparrow 3 = 3 \uparrow\uparrow(3 \uparrow\uparrow 3) = 3 \uparrow\uparrow( 3 \uparrow 3 \uparrow 3)$$

## Source code

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## Questions / Comments

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Source : https://www.dcode.fr/knuth-arrows
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