Can someone explain why
\sum_{k=1}^\infty (ζ[2k+1]-1)=\frac{1}{4}?
Answer
We can rearrange
\begin{align}\sum_{k=1}^\infty(\zeta(2k+1)-1)&=\sum_{k=1}^\infty\sum_{n=2}^\infty\frac1{n^{2k+1}}\\ &=\sum_{n=2}^\infty\sum_{k=1}^\infty\frac1{n^{2k+1}}\\ &=\sum_{n=2}^\infty\frac1{n(n^2-1)}\\ &=\sum_{n=2}^\infty\left(\frac1{2n(n-1)}-\frac1{2(n+1)n}\right)\\&=\frac14\end{align}
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