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.

Knuth's Arrows - dCode

Tag(s) : Arithmetics, Notation System

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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.

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 ( \( 2^3 = 2 \times 2 \times 2 \) ), 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.

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

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

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