Bernoulli polynomials

In mathematics, the Bernoulli polynomials, named after Jacob Bernoulli, combine the Bernoulli numbers and binomial coefficients. They are used for series expansion of functions, and with the Euler–MacLaurin formula.

These polynomials occur in the study of many special functions and, in particular the Riemann zeta function and the Hurwitz zeta function. They are an Appell sequence (i.e. a Sheffer sequence for the ordinary derivative operator). For the Bernoulli polynomials, the number of crossings of the x-axis in the unit interval does not go up with the degree. In the limit of large degree, they approach, when appropriately scaled, the sine and cosine functions.

Bernoulli polynomials

A similar set of polynomials, based on a generating function, is the family of Euler polynomials.


The Bernoulli polynomials Bn can be defined by a generating function. They also admit a variety of derived representations.

Generating functionsEdit

The generating function for the Bernoulli polynomials is


The generating function for the Euler polynomials is


Explicit formulaEdit


for n ≥ 0, where Bk are the Bernoulli numbers, and Ek are the Euler numbers.

Representation by a differential operatorEdit

The Bernoulli polynomials are also given by


where D = d/dx is differentiation with respect to x and the fraction is expanded as a formal power series. It follows that


cf. integrals below. By the same token, the Euler polynomials are given by


Representation by an integral operatorEdit

The Bernoulli polynomials are also the unique polynomials determined by


The integral transform


on polynomials f, simply amounts to


This can be used to produce the inversion formulae below.

Another explicit formulaEdit

An explicit formula for the Bernoulli polynomials is given by


That is similar to the series expression for the Hurwitz zeta function in the complex plane. Indeed, there is the relationship


where ζ(sq) is the Hurwitz zeta function. The latter generalizes the Bernoulli polynomials, allowing for non-integer values of n.

The inner sum may be understood to be the nth forward difference of xm; that is,


where Δ is the forward difference operator. Thus, one may write


This formula may be derived from an identity appearing above as follows. Since the forward difference operator Δ equals


where D is differentiation with respect to x, we have, from the Mercator series,


As long as this operates on an mth-degree polynomial such as xm, one may let n go from 0 only up to m.

An integral representation for the Bernoulli polynomials is given by the Nörlund–Rice integral, which follows from the expression as a finite difference.

An explicit formula for the Euler polynomials is given by


The above follows analogously, using the fact that


Sums of pth powersEdit

Using either the above integral representation of   or the identity  , we have


(assuming 00 = 1). See Faulhaber's formula for more on this.

The Bernoulli and Euler numbersEdit

The Bernoulli numbers are given by  

This definition gives   for  .

An alternate convention defines the Bernoulli numbers as  

The two conventions differ only for   since  .

The Euler numbers are given by  

Explicit expressions for low degreesEdit

The first few Bernoulli polynomials are:


The first few Euler polynomials are:


Maximum and minimumEdit

At higher n, the amount of variation in Bn(x) between x = 0 and x = 1 gets large. For instance,


which shows that the value at x = 0 (and at x = 1) is −3617/510 ≈ −7.09, while at x = 1/2, the value is 118518239/3342336 ≈ +7.09. D.H. Lehmer[1] showed that the maximum value of Bn(x) between 0 and 1 obeys


unless n is 2 modulo 4, in which case


(where   is the Riemann zeta function), while the minimum obeys


unless n is 0 modulo 4, in which case


These limits are quite close to the actual maximum and minimum, and Lehmer gives more accurate limits as well.

Differences and derivativesEdit

The Bernoulli and Euler polynomials obey many relations from umbral calculus:


(Δ is the forward difference operator). Also,


These polynomial sequences are Appell sequences:




These identities are also equivalent to saying that these polynomial sequences are Appell sequences. (Hermite polynomials are another example.)



Zhi-Wei Sun and Hao Pan [2] established the following surprising symmetry relation: If r + s + t = n and x + y + z = 1, then




Fourier seriesEdit

The Fourier series of the Bernoulli polynomials is also a Dirichlet series, given by the expansion


Note the simple large n limit to suitably scaled trigonometric functions.

This is a special case of the analogous form for the Hurwitz zeta function


This expansion is valid only for 0 ≤ x ≤ 1 when n ≥ 2 and is valid for 0 < x < 1 when n = 1.

The Fourier series of the Euler polynomials may also be calculated. Defining the functions




for  , the Euler polynomial has the Fourier series




Note that the   and   are odd and even, respectively:




They are related to the Legendre chi function   as





The Bernoulli and Euler polynomials may be inverted to express the monomial in terms of the polynomials.

Specifically, evidently from the above section on integral operators, it follows that




Relation to falling factorialEdit

The Bernoulli polynomials may be expanded in terms of the falling factorial   as


where   and


denotes the Stirling number of the second kind. The above may be inverted to express the falling factorial in terms of the Bernoulli polynomials:




denotes the Stirling number of the first kind.

Multiplication theoremsEdit

The multiplication theorems were given by Joseph Ludwig Raabe in 1851:

For a natural number m≥1,



Two definite integrals relating the Bernoulli and Euler polynomials to the Bernoulli and Euler numbers are:[citation needed]


Periodic Bernoulli polynomialsEdit

A periodic Bernoulli polynomial Pn(x) is a Bernoulli polynomial evaluated at the fractional part of the argument x. These functions are used to provide the remainder term in the Euler–Maclaurin formula relating sums to integrals. The first polynomial is a sawtooth function.

Strictly these functions are not polynomials at all and more properly should be termed the periodic Bernoulli functions, and P0(x) is not even a function, being the derivative of a sawtooth and so a Dirac comb.

The following properties are of interest, valid for all  :


See alsoEdit


  1. ^ D.H. Lehmer, "On the Maxima and Minima of Bernoulli Polynomials", American Mathematical Monthly, volume 47, pages 533–538 (1940)
  2. ^ Zhi-Wei Sun; Hao Pan (2006). "Identities concerning Bernoulli and Euler polynomials". Acta Arithmetica. 125: 21–39. arXiv:math/0409035. Bibcode:2006AcAri.125...21S. doi:10.4064/aa125-1-3.

External linksEdit