= Harmonic power of a square wave
{title2=$P_{\{r,-r\}}/P=8/(\pi^2r^2),\quad r\text{ odd}$}
A zero-mean <square wave> of <amplitude> $G$ has total <mean-square signal power> $G^2$. Each positive odd <Fourier harmonic> and its negative-frequency partner contribute $8G^2/(\pi^2r^2)$, by its exact <Fourier coefficients>. The fundamental pair therefore accounts for $8/\pi^2$ of the total. The sum of contributions above harmonic index $R$ decays on the order of $R^{-1}$, although the discontinuous waveform still requires arbitrarily high harmonics for exact reconstruction.
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