I work at the Science Museum on weekends, and I sometimes present the following puzzle:
$$0\;0 \; 0 = 6$$ $$1 \; 1 \; 1 = 6$$ $$2 \; 2 \; 2 = 6$$ $$3 \;3 \; 3 = 6$$ $$\vdots$$ $$n\;n\;n=6$$ The idea is you can add in any operations you like, as long as they do not require you to write additional numbers. For example:
$$2 + 2 + 2 =6$$ $$\sqrt4+\sqrt4+\sqrt4=6$$ $$ (1+1+1)! = 6$$ But $\sqrt[3]{8}+\sqrt[3]{8}+\sqrt[3]{8}=6$ would not be allowed, as it requires the additional three to be written.
The operations are thus typically restricted to $+\;-\;\times\;\div\;\sqrt\;\;!$
I have solutions for every integer n so $0\le n\le10$ (available at request), and for every integer $n^{2k}$ where $k\in{\mathbb{N}}$ (this is accomplished by nesting square roots.)
My question is two parts:
- Is there any other integers for which there are solutions?
- Are there any other operations that I haven't used that can be used to solve the problems in creative ways?
$\sqrt{35+35/35}=6$ This can be extended to $6^{2n}-1$ with more square roots. $16/\sqrt{16}+\sqrt{\sqrt{16}}=6\\144/(\sqrt{144}+\sqrt{144})=6$
Other operators I have seen are concatenation, so $\sqrt {33+3}=6$ (though you probably have $3 \times 3-3=6$), decimals (so you can get $.2$ instead of $2$ and now $94/.94-94=6$), repeats (so you can do $.\overline 2=\frac 29$) and the floor function. Floor plus factorial is too powerful-I remember seeing a proof that those plus a single $\pi$ could give any natural. You might want to include base $2$ logs-I have seen $\lg(x)$ but the ISO version seems to be $\operatorname{lb}(x)$.