Introduction of an Elementary Method to Express $\zeta (2n+1)$ in Terms of $\zeta (2k)$ with $k\ge 1$

In this note we give the most elementary method (as far as we know) to express $\zeta (2n+1)$ in terms of $\{\zeta (2k)\mathrm{\mid }k\ge 1\}$. The method is based on only some elementary works by Leonhard Euler, so it is very instructive to non-experts or students.