**I. Comparison**

It doesn't seem to be well-known that the generic cubic (prominent in this [MO post][1]) for $C_3 = A_3$,

$$x^3-nx^2+(n-3)x+1 = 0$$

has the nice property that its roots $a,b,c$, if in correct order, obey,

$$(a^2b)^{1/3}+(b^2c)^{1/3}+(c^2a)^{1/3} = 0$$

(I only noticed this after I asked an [MO question][2] about the similar-looking Klein quartic $a^3b+b^3c+c^3a=0.$)

Since the generic cubic is intimately connected to the roots of unity for prime $p\equiv 1\,\text{mod}\; 6$, (the case $n=1$ yields $1^{1/7}$), naturally I got curious about its big sister the *Emma Lehmer quintic* which is for $p\equiv 1\,\text{mod}\; 10$, namely,

$$x^5 + n^2x^4 - (2n^3 + 6n^2 + 10n + 10)x^3 + (n^4 + 5n^3 + 11n^2 + 15n + 5)x^2 + (n^3 + 4n^2 + 10n + 10)x +1=0$$

It turns out its roots $x_k$ may have a similar property. 

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**II. Question:** 

Analogous to the generic cubic, is it true that the Emma Lehmer quintic obeys, $$(a^4b^3c^2d)^{1/5} + (b^4c^3d^2e)^{1/5} + (c^4d^3e^2a)^{1/5} + (d^4e^3a^2b)^{1/5} + (e^4a^3b^2c)^{1/5} = 0$$ for the **correct** ordering of its roots $a,b,c,d,e$? 

**Update:** Thanks to Peter Taylor in the comments, and using the fact that $abcde = -1$, we can get rid of the fifth roots and get the equivalent but more elegant form,

$$\frac1{a}-\frac1{ab}+\frac1{abc}-\frac1{abcd}+\frac1{abcde} = 0$$

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**III. Example** 

Let $n=-1$. Then we get the quintic for $p=11$ and its roots,

$$x^5 + x^4 - 4x^3 - 3x^2 + 3x + 1 = 0$$

$$a,b,c,d,e = 2\cos\frac{2\pi k}{11}$$

with $k = 1, 4, 5, 2, 3$ as the correct order. One can then verify it obeys the relation in the question.
 
**P.S.** For $p=5$, there are $(p-1)! = 24$ permutations of its roots. It is easy for a computer to find the correct order for any $n$ that I tested. But does it hold true for ALL $n$?   


  [1]: https://mathoverflow.net/questions/438594/
  [2]: https://mathoverflow.net/questions/438035/