Four Fours/13/Solutions/4

Puzzle: Four Fours: $13$

Using exactly $4$ instances of the number $4$, the task is to write an expression for $13$, using whatever arithmetical operations you consider necessary.

Solution

$13 = \map \Gamma 4 \times \sqrt 4 + \dfrac 4 4$

where $\Gamma$ is the gamma function: $\map \Gamma 4 = 6$

Sources

• 1980: Angela Dunn: Mathematical Bafflers (revised ed.) ... (previous) ... (next): $1$. Say it with Letters: Algebraic Amusements: Four Fours