To those who are interested:

New version of FourierTrigSeries package was released. This release fixes a bug in ExploreFourierSeriesCoefficients procedure.

FourierTrigSeries package provides new data structure for the representation of trigonometric series and also several procedures to manipulate with trigonometric series and to compute Fourier series.

Visit the homepage and see some examples. Try also the online Fourier series calculator.