itilbert(x, h, period=2*pi) -> y
Return inverse h-Tilbert transform of a periodic sequence x.
If x_j and y_j are Fourier coefficients of periodic functions x and y, respectively, then
y_j = -sqrt(-1)*tanh(j*h*2*pi/period) * x_j y_0 = 0
Optional input: see tilbert.__doc__