For a periodic square wave, which one of the following statements

1. The Fourier series coefficients do not exist
2. The Fourier series coefficients exist but the reconstruction converges at no point
3. The Fourier series coefficients exist and the reconstruction converges at most points.
4. The Fourier series coefficients exist and the reconstruction converges at every point

For a Periodic square wave, the fourier series coefficients exist and reconstruction converges at most points.