Fejér polynomial

A trigonometric polynomial of the form

$$\sum_{k=1}^n\frac1k(\cos(2n+k)x-\cos(2n-k)x),$$

or a similar polynomial in sines. Fejér polynomials are used in constructing continuous functions for which their Fourier series have given singularities.

References

[1]	N.K. [N.K. Bari] Bary, "A treatise on trigonometric series" , Pergamon (1964) (Translated from Russian) MR0171116 Zbl 0129.28002