The Sierpinski's conjecture states that for all integer $n>1$, we have $\frac{5}{n}=\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$ where $(a,b,c) \in \mathbb{N}_*^3$.
But is it easier to prove that $\frac{5}{n}=\frac{1}{a}+\frac{1}{b}+\frac{1}{c}+\frac{1}{d}$ ?
Thanks,
B.L.