Another elementary proof of $\: \sum_{n \ge 1}{1/{n^2}} = \pi^2/6\,$ and a recurrence formula for $\,\zeta{(2k)}$

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Abstract

In this shortnote, a series expansion technique introduced recently by Dancs and He for generating Euler-type formulae for odd zeta values $\:\zeta{(2 k +1)}$, $\zeta{(s)}$ being the Riemann zeta function and $k$ a positive integer, is modified in a manner to furnish the even zeta values $ \zeta{(2k)}$. As a result, I find an elementary proof of $\sum_{n=1}^\infty{{1/{n^2}}} = {\pi^2/6}$, as well as a recurrence formula for $\zeta{(2k)}$ from which it follows that the ratio ${\zeta{(2k)} / \pi^{2k}}$ is a rational number, without making use of Euler's formula and Bernoulli numbers.