In mathematics , the Bernoulli polynomials occur in the study of many special functions and in particular the Riemann zeta function and the Hurwitz zeta function . This is in large part because they are an Appell sequence , i.e. a Sheffer sequence for the ordinary derivative operator. Unlike orthogonal polynomials , the Bernoulli polynomials are remarkable in that the number of crossings of the x -axis in the unit interval does not go up as the degree of the polynomials goes up. In the limit of large degree, the Bernoulli polynomials, appropriately scaled, approach the sine and cosine functions .
Bernoulli polynomials
This article also discusses the Bernoulli polynomials and the related Euler polynomials, and the Bernoulli and Euler numbers .
Representations
The Bernoulli polynomials B n admit a variety of different representations . Which among them should be taken to be the definition may depend on one's purposes.
Explicit formula
B
n
(
x
)
=
∑
k
=
0
n
(
n
k
)
b
n
−
k
x
k
,
{\displaystyle B_{n}(x)=\sum _{k=0}^{n}{n \choose k}b_{n-k}x^{k},}
for n ≥ 0, where b k are the Bernoulli numbers .
Generating functions
The generating function for the Bernoulli polynomials is
t
e
x
t
e
t
−
1
=
∑
n
=
0
∞
B
n
(
x
)
t
n
n
!
.
{\displaystyle {\frac {te^{xt}}{e^{t}-1}}=\sum _{n=0}^{\infty }B_{n}(x){\frac {t^{n}}{n!}}.}
The generating function for the Euler polynomials is
2
e
x
t
e
t
+
1
=
∑
n
=
0
∞
E
n
(
x
)
t
n
n
!
.
{\displaystyle {\frac {2e^{xt}}{e^{t}+1}}=\sum _{n=0}^{\infty }E_{n}(x){\frac {t^{n}}{n!}}.}
Representation by a differential operator
The Bernoulli polynomials are also given by
B
n
(
x
)
=
D
e
D
−
1
x
n
{\displaystyle B_{n}(x)={D \over e^{D}-1}x^{n}}
where D = d /dx is differentiation with respect to x and the fraction is expanded as a formal power series . It follows that
∫
a
x
B
n
(
u
)
d
u
=
B
n
+
1
(
x
)
−
B
n
+
1
(
a
)
n
+
1
.
{\displaystyle \int _{a}^{x}B_{n}(u)~du={\frac {B_{n+1}(x)-B_{n+1}(a)}{n+1}}~.}
cf. integrals below .
Representation by an integral operator
The Bernoulli polynomials are the unique polynomials determined by
∫
x
x
+
1
B
n
(
u
)
d
u
=
x
n
.
{\displaystyle \int _{x}^{x+1}B_{n}(u)\,du=x^{n}.}
The integral transform
(
T
f
)
(
x
)
=
∫
x
x
+
1
f
(
u
)
d
u
{\displaystyle (Tf)(x)=\int _{x}^{x+1}f(u)\,du}
on polynomials f , simply amounts to
(
T
f
)
(
x
)
=
e
D
−
1
D
f
(
x
)
=
∑
n
=
0
∞
D
n
(
n
+
1
)
!
f
(
x
)
=
f
(
x
)
+
f
′
(
x
)
2
+
f
″
(
x
)
6
+
f
‴
(
x
)
24
+
⋯
.
{\displaystyle {\begin{aligned}(Tf)(x)={e^{D}-1 \over D}f(x)&{}=\sum _{n=0}^{\infty }{D^{n} \over (n+1)!}f(x)\\&{}=f(x)+{f'(x) \over 2}+{f''(x) \over 6}+{f'''(x) \over 24}+\cdots ~.\end{aligned}}}
This can be used to produce the inversion formulae below .
Another explicit formula
An explicit formula for the Bernoulli polynomials is given by
B
m
(
x
)
=
∑
n
=
0
m
1
n
+
1
∑
k
=
0
n
(
−
1
)
k
(
n
k
)
(
x
+
k
)
m
.
{\displaystyle B_{m}(x)=\sum _{n=0}^{m}{\frac {1}{n+1}}\sum _{k=0}^{n}(-1)^{k}{n \choose k}(x+k)^{m}.}
Note the remarkable similarity to the globally convergent series expression for the Hurwitz zeta function . Indeed, one has
B
n
(
x
)
=
−
n
ζ
(
1
−
n
,
x
)
{\displaystyle B_{n}(x)=-n\zeta (1-n,x)}
where ζ (s , q ) is the Hurwitz zeta; thus, in a certain sense, the Hurwitz zeta generalizes the Bernoulli polynomials to non-integer values of n .
The inner sum may be understood to be the n th forward difference of x m ; that is,
Δ
n
x
m
=
∑
k
=
0
n
(
−
1
)
n
−
k
(
n
k
)
(
x
+
k
)
m
{\displaystyle \Delta ^{n}x^{m}=\sum _{k=0}^{n}(-1)^{n-k}{n \choose k}(x+k)^{m}}
where Δ is the forward difference operator . Thus, one may write
B
m
(
x
)
=
∑
n
=
0
m
(
−
1
)
n
n
+
1
Δ
n
x
m
.
{\displaystyle B_{m}(x)=\sum _{n=0}^{m}{\frac {(-1)^{n}}{n+1}}\Delta ^{n}x^{m}.}
This formula may be derived from an identity appearing above as follows. Since the forward difference operator Δ equals
Δ
=
e
D
−
1
{\displaystyle \Delta =e^{D}-1\,}
where D is differentiation with respect to x , we have, from the Mercator series
D
e
D
−
1
=
log
(
Δ
+
1
)
Δ
=
∑
n
=
0
∞
(
−
Δ
)
n
n
+
1
.
{\displaystyle {D \over e^{D}-1}={\log(\Delta +1) \over \Delta }=\sum _{n=0}^{\infty }{(-\Delta )^{n} \over n+1}.}
As long as this operates on an m th-degree polynomial such as x m , 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
E
m
(
x
)
=
∑
n
=
0
m
1
2
n
∑
k
=
0
n
(
−
1
)
k
(
n
k
)
(
x
+
k
)
m
.
{\displaystyle E_{m}(x)=\sum _{n=0}^{m}{\frac {1}{2^{n}}}\sum _{k=0}^{n}(-1)^{k}{n \choose k}(x+k)^{m}\,.}
This may also be written in terms of the Euler numbers E k as
E
m
(
x
)
=
∑
k
=
0
m
(
m
k
)
E
k
2
k
(
x
−
1
2
)
m
−
k
.
{\displaystyle E_{m}(x)=\sum _{k=0}^{m}{m \choose k}{\frac {E_{k}}{2^{k}}}\left(x-{\frac {1}{2}}\right)^{m-k}\,.}
Sums of p th powers
We have
∑
k
=
0
x
k
p
=
B
p
+
1
(
x
+
1
)
−
B
p
+
1
(
0
)
p
+
1
{\displaystyle \sum _{k=0}^{x}k^{p}={\frac {B_{p+1}(x+1)-B_{p+1}(0)}{p+1}}}
(assuming 00 =1). See Faulhaber's formula for more on this.
The Bernoulli and Euler numbers
The Bernoulli numbers are given by
B
n
=
B
n
(
0
)
.
{\displaystyle \textstyle B_{n}=B_{n}(0).}
This definition gives
ζ
(
−
n
)
=
−
1
n
+
1
B
n
+
1
{\displaystyle \textstyle \zeta (-n)=-{\frac {1}{n+1}}B_{n+1}}
for
n
=
0
,
1
,
2
,
…
{\displaystyle \textstyle n=0,1,2,\ldots }
.
An alternate convention defines the Bernoulli numbers as
B
n
=
B
n
(
1
)
.
{\displaystyle \textstyle B_{n}=B_{n}(1).}
The two conventions differ only for
n
=
1
{\displaystyle n=1}
since
B
1
(
1
)
=
1
2
=
−
B
1
(
0
)
{\displaystyle B_{1}(1)={\frac {1}{2}}=-B_{1}(0)}
.
The Euler numbers are given by
E
n
=
2
n
E
n
(
1
2
)
.
{\displaystyle E_{n}=2^{n}E_{n}({\frac {1}{2}}).}
Explicit expressions for low degrees
The first few Bernoulli polynomials are:
B
0
(
x
)
=
1
B
1
(
x
)
=
x
−
1
2
B
2
(
x
)
=
x
2
−
x
+
1
6
B
3
(
x
)
=
x
3
−
3
2
x
2
+
1
2
x
B
4
(
x
)
=
x
4
−
2
x
3
+
x
2
−
1
30
B
5
(
x
)
=
x
5
−
5
2
x
4
+
5
3
x
3
−
1
6
x
B
6
(
x
)
=
x
6
−
3
x
5
+
5
2
x
4
−
1
2
x
2
+
1
42
.
{\displaystyle {\begin{aligned}B_{0}(x)&=1\\[8pt]B_{1}(x)&=x-{\frac {1}{2}}\\[8pt]B_{2}(x)&=x^{2}-x+{\frac {1}{6}}\\[8pt]B_{3}(x)&=x^{3}-{\frac {3}{2}}x^{2}+{\frac {1}{2}}x\\[8pt]B_{4}(x)&=x^{4}-2x^{3}+x^{2}-{\frac {1}{30}}\\[8pt]B_{5}(x)&=x^{5}-{\frac {5}{2}}x^{4}+{\frac {5}{3}}x^{3}-{\frac {1}{6}}x\\[8pt]B_{6}(x)&=x^{6}-3x^{5}+{\frac {5}{2}}x^{4}-{\frac {1}{2}}x^{2}+{\frac {1}{42}}.\end{aligned}}}
The first few Euler polynomials are:
E
0
(
x
)
=
1
E
1
(
x
)
=
x
−
1
2
E
2
(
x
)
=
x
2
−
x
E
3
(
x
)
=
x
3
−
3
2
x
2
+
1
4
E
4
(
x
)
=
x
4
−
2
x
3
+
x
E
5
(
x
)
=
x
5
−
5
2
x
4
+
5
2
x
2
−
1
2
E
6
(
x
)
=
x
6
−
3
x
5
+
5
x
3
−
3
x
.
{\displaystyle {\begin{aligned}E_{0}(x)&=1\\[8pt]E_{1}(x)&=x-{\frac {1}{2}}\\[8pt]E_{2}(x)&=x^{2}-x\\[8pt]E_{3}(x)&=x^{3}-{\frac {3}{2}}x^{2}+{\frac {1}{4}}\\[8pt]E_{4}(x)&=x^{4}-2x^{3}+x\\[8pt]E_{5}(x)&=x^{5}-{\frac {5}{2}}x^{4}+{\frac {5}{2}}x^{2}-{\frac {1}{2}}\\[8pt]E_{6}(x)&=x^{6}-3x^{5}+5x^{3}-3x.\end{aligned}}}
Maximum and minimum
At higher n , the amount of variation in B n (x ) between x = 0 and x = 1 gets large. For instance,
B
16
(
x
)
=
x
16
−
8
x
15
+
20
x
14
−
182
3
x
12
+
572
3
x
10
−
429
x
8
+
1820
3
x
6
−
1382
3
x
4
+
140
x
2
−
3617
510
{\displaystyle B_{16}(x)=x^{16}-8x^{15}+20x^{14}-{\frac {182}{3}}x^{12}+{\frac {572}{3}}x^{10}-429x^{8}+{\frac {1820}{3}}x^{6}-{\frac {1382}{3}}x^{4}+140x^{2}-{\frac {3617}{510}}}
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 B n (x ) between 0 and 1 obeys
M
n
<
2
n
!
(
2
π
)
n
{\displaystyle M_{n}<{\frac {2n!}{(2\pi )^{n}}}}
unless n is 2 modulo 4, in which case
M
n
=
2
ζ
(
n
)
n
!
(
2
π
)
n
{\displaystyle M_{n}={\frac {2\zeta (n)n!}{(2\pi )^{n}}}}
(where
ζ
(
x
)
{\displaystyle \zeta (x)}
is the Riemann zeta function ), while the minimum obeys
m
n
>
−
2
n
!
(
2
π
)
n
{\displaystyle m_{n}>{\frac {-2n!}{(2\pi )^{n}}}}
unless n is 0 modulo 4, in which case
m
n
=
−
2
ζ
(
n
)
n
!
(
2
π
)
n
.
{\displaystyle m_{n}={\frac {-2\zeta (n)n!}{(2\pi )^{n}}}.}
These limits are quite close to the actual maximum and minimum, and Lehmer gives more accurate limits as well.
Differences and derivatives
The Bernoulli and Euler polynomials obey many relations from umbral calculus :
Δ
B
n
(
x
)
=
B
n
(
x
+
1
)
−
B
n
(
x
)
=
n
x
n
−
1
,
{\displaystyle \Delta B_{n}(x)=B_{n}(x+1)-B_{n}(x)=nx^{n-1},\,}
Δ
E
n
(
x
)
=
E
n
(
x
+
1
)
−
E
n
(
x
)
=
2
(
x
n
−
E
n
(
x
)
)
.
{\displaystyle \Delta E_{n}(x)=E_{n}(x+1)-E_{n}(x)=2(x^{n}-E_{n}(x)).\,}
(Δ is the forward difference operator ).
These polynomial sequences are Appell sequences :
B
n
′
(
x
)
=
n
B
n
−
1
(
x
)
,
{\displaystyle B_{n}'(x)=nB_{n-1}(x),\,}
E
n
′
(
x
)
=
n
E
n
−
1
(
x
)
.
{\displaystyle E_{n}'(x)=nE_{n-1}(x).\,}
Translations
B
n
(
x
+
y
)
=
∑
k
=
0
n
(
n
k
)
B
k
(
x
)
y
n
−
k
{\displaystyle B_{n}(x+y)=\sum _{k=0}^{n}{n \choose k}B_{k}(x)y^{n-k}}
E
n
(
x
+
y
)
=
∑
k
=
0
n
(
n
k
)
E
k
(
x
)
y
n
−
k
{\displaystyle E_{n}(x+y)=\sum _{k=0}^{n}{n \choose k}E_{k}(x)y^{n-k}}
These identities are also equivalent to saying that these polynomial sequences are Appell sequences . (Hermite polynomials are another example.)
Symmetries
B
n
(
1
−
x
)
=
(
−
1
)
n
B
n
(
x
)
,
n
≥
0
,
{\displaystyle B_{n}(1-x)=(-1)^{n}B_{n}(x),\quad n\geq 0,}
E
n
(
1
−
x
)
=
(
−
1
)
n
E
n
(
x
)
{\displaystyle E_{n}(1-x)=(-1)^{n}E_{n}(x)\,}
(
−
1
)
n
B
n
(
−
x
)
=
B
n
(
x
)
+
n
x
n
−
1
{\displaystyle (-1)^{n}B_{n}(-x)=B_{n}(x)+nx^{n-1}\,}
(
−
1
)
n
E
n
(
−
x
)
=
−
E
n
(
x
)
+
2
x
n
{\displaystyle (-1)^{n}E_{n}(-x)=-E_{n}(x)+2x^{n}\,}
B
n
(
1
2
)
=
(
1
2
n
−
1
−
1
)
B
n
,
n
≥
0
from the multiplication theorems below.
{\displaystyle B_{n}\left({\frac {1}{2}}\right)=\left({\frac {1}{2^{n-1}}}-1\right)B_{n},\quad n\geq 0{\text{ from the multiplication theorems below.}}}
Zhi-Wei Sun and Hao Pan [2] established the following surprising symmetry relation: If r + s + t = n and x + y + z = 1 , then
r
[
s
,
t
;
x
,
y
]
n
+
s
[
t
,
r
;
y
,
z
]
n
+
t
[
r
,
s
;
z
,
x
]
n
=
0
,
{\displaystyle r[s,t;x,y]_{n}+s[t,r;y,z]_{n}+t[r,s;z,x]_{n}=0,}
where
[
s
,
t
;
x
,
y
]
n
=
∑
k
=
0
n
(
−
1
)
k
(
s
k
)
(
t
n
−
k
)
B
n
−
k
(
x
)
B
k
(
y
)
.
{\displaystyle [s,t;x,y]_{n}=\sum _{k=0}^{n}(-1)^{k}{s \choose k}{t \choose {n-k}}B_{n-k}(x)B_{k}(y).}
Fourier series
The Fourier series of the Bernoulli polynomials is also a Dirichlet series , given by the expansion
B
n
(
x
)
=
−
n
!
(
2
π
i
)
n
∑
k
≠
0
e
2
π
i
k
x
k
n
=
−
2
n
!
∑
k
=
1
∞
cos
(
2
k
π
x
−
n
π
2
)
(
2
k
π
)
n
.
{\displaystyle B_{n}(x)=-{\frac {n!}{(2\pi i)^{n}}}\sum _{k\not =0}{\frac {e^{2\pi ikx}}{k^{n}}}=-2n!\sum _{k=1}^{\infty }{\frac {\cos \left(2k\pi x-{\frac {n\pi }{2}}\right)}{(2k\pi )^{n}}}.}
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
B
n
(
x
)
=
−
Γ
(
n
+
1
)
∑
k
=
1
∞
exp
(
2
π
i
k
x
)
+
e
i
π
n
exp
(
2
π
i
k
(
1
−
x
)
)
(
2
π
i
k
)
n
.
{\displaystyle B_{n}(x)=-\Gamma (n+1)\sum _{k=1}^{\infty }{\frac {\exp(2\pi ikx)+e^{i\pi n}\exp(2\pi ik(1-x))}{(2\pi ik)^{n}}}.}
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
C
ν
(
x
)
=
∑
k
=
0
∞
cos
(
(
2
k
+
1
)
π
x
)
(
2
k
+
1
)
ν
{\displaystyle C_{\nu }(x)=\sum _{k=0}^{\infty }{\frac {\cos((2k+1)\pi x)}{(2k+1)^{\nu }}}}
and
S
ν
(
x
)
=
∑
k
=
0
∞
sin
(
(
2
k
+
1
)
π
x
)
(
2
k
+
1
)
ν
{\displaystyle S_{\nu }(x)=\sum _{k=0}^{\infty }{\frac {\sin((2k+1)\pi x)}{(2k+1)^{\nu }}}}
for
ν
>
1
{\displaystyle \nu >1}
, the Euler polynomial has the Fourier series
C
2
n
(
x
)
=
(
−
1
)
n
4
(
2
n
−
1
)
!
π
2
n
E
2
n
−
1
(
x
)
{\displaystyle C_{2n}(x)={\frac {(-1)^{n}}{4(2n-1)!}}\pi ^{2n}E_{2n-1}(x)}
and
S
2
n
+
1
(
x
)
=
(
−
1
)
n
4
(
2
n
)
!
π
2
n
+
1
E
2
n
(
x
)
.
{\displaystyle S_{2n+1}(x)={\frac {(-1)^{n}}{4(2n)!}}\pi ^{2n+1}E_{2n}(x).}
Note that the
C
ν
{\displaystyle C_{\nu }}
and
S
ν
{\displaystyle S_{\nu }}
are odd and even, respectively:
C
ν
(
x
)
=
−
C
ν
(
1
−
x
)
{\displaystyle C_{\nu }(x)=-C_{\nu }(1-x)}
and
S
ν
(
x
)
=
S
ν
(
1
−
x
)
.
{\displaystyle S_{\nu }(x)=S_{\nu }(1-x).}
They are related to the Legendre chi function
χ
ν
{\displaystyle \chi _{\nu }}
as
C
ν
(
x
)
=
Re
χ
ν
(
e
i
x
)
{\displaystyle C_{\nu }(x)={\mbox{Re}}\chi _{\nu }(e^{ix})}
and
S
ν
(
x
)
=
Im
χ
ν
(
e
i
x
)
.
{\displaystyle S_{\nu }(x)={\mbox{Im}}\chi _{\nu }(e^{ix}).}
Inversion
The Bernoulli and Euler polynomials may be inverted to express the monomial in terms of the polynomials.
Specifically, evidently from the above section on #Representation by an integral operator , it follows that
x
n
=
1
n
+
1
∑
k
=
0
n
(
n
+
1
k
)
B
k
(
x
)
{\displaystyle x^{n}={\frac {1}{n+1}}\sum _{k=0}^{n}{n+1 \choose k}B_{k}(x)}
and
x
n
=
E
n
(
x
)
+
1
2
∑
k
=
0
n
−
1
(
n
k
)
E
k
(
x
)
.
{\displaystyle x^{n}=E_{n}(x)+{\frac {1}{2}}\sum _{k=0}^{n-1}{n \choose k}E_{k}(x).}
Relation to falling factorial
The Bernoulli polynomials may be expanded in terms of the falling factorial
(
x
)
k
{\displaystyle (x)_{k}}
as
B
n
+
1
(
x
)
=
B
n
+
1
+
∑
k
=
0
n
n
+
1
k
+
1
{
n
k
}
(
x
)
k
+
1
{\displaystyle B_{n+1}(x)=B_{n+1}+\sum _{k=0}^{n}{\frac {n+1}{k+1}}\left\{{\begin{matrix}n\\k\end{matrix}}\right\}(x)_{k+1}}
where
B
n
=
B
n
(
0
)
{\displaystyle B_{n}=B_{n}(0)}
and
{
n
k
}
=
S
(
n
,
k
)
{\displaystyle \left\{{\begin{matrix}n\\k\end{matrix}}\right\}=S(n,k)}
denotes the Stirling number of the second kind . The above may be inverted to express the falling factorial in terms of the Bernoulli polynomials:
(
x
)
n
+
1
=
∑
k
=
0
n
n
+
1
k
+
1
[
n
k
]
(
B
k
+
1
(
x
)
−
B
k
+
1
)
{\displaystyle (x)_{n+1}=\sum _{k=0}^{n}{\frac {n+1}{k+1}}\left[{\begin{matrix}n\\k\end{matrix}}\right]\left(B_{k+1}(x)-B_{k+1}\right)}
where
[
n
k
]
=
s
(
n
,
k
)
{\displaystyle \left[{\begin{matrix}n\\k\end{matrix}}\right]=s(n,k)}
denotes the Stirling number of the first kind .
Multiplication theorems
The multiplication theorems were given by Joseph Ludwig Raabe in 1851:
For a natural number m ≥1 ,
B
n
(
m
x
)
=
m
n
−
1
∑
k
=
0
m
−
1
B
n
(
x
+
k
m
)
{\displaystyle B_{n}(mx)=m^{n-1}\sum _{k=0}^{m-1}B_{n}\left(x+{\frac {k}{m}}\right)}
E
n
(
m
x
)
=
m
n
∑
k
=
0
m
−
1
(
−
1
)
k
E
n
(
x
+
k
m
)
for
m
=
1
,
3
,
…
{\displaystyle E_{n}(mx)=m^{n}\sum _{k=0}^{m-1}(-1)^{k}E_{n}\left(x+{\frac {k}{m}}\right)\quad {\mbox{ for }}m=1,3,\dots }
E
n
(
m
x
)
=
−
2
n
+
1
m
n
∑
k
=
0
m
−
1
(
−
1
)
k
B
n
+
1
(
x
+
k
m
)
for
m
=
2
,
4
,
…
{\displaystyle E_{n}(mx)={\frac {-2}{n+1}}m^{n}\sum _{k=0}^{m-1}(-1)^{k}B_{n+1}\left(x+{\frac {k}{m}}\right)\quad {\mbox{ for }}m=2,4,\dots }
Integrals
Indefinite integrals
∫
a
x
B
n
(
t
)
d
t
=
B
n
+
1
(
x
)
−
B
n
+
1
(
a
)
n
+
1
{\displaystyle \int _{a}^{x}B_{n}(t)\,dt={\frac {B_{n+1}(x)-B_{n+1}(a)}{n+1}}}
∫
a
x
E
n
(
t
)
d
t
=
E
n
+
1
(
x
)
−
E
n
+
1
(
a
)
n
+
1
{\displaystyle \int _{a}^{x}E_{n}(t)\,dt={\frac {E_{n+1}(x)-E_{n+1}(a)}{n+1}}}
Definite integrals
∫
0
1
B
n
(
t
)
B
m
(
t
)
d
t
=
(
−
1
)
n
−
1
m
!
n
!
(
m
+
n
)
!
B
n
+
m
for
m
,
n
≥
1
{\displaystyle \int _{0}^{1}B_{n}(t)B_{m}(t)\,dt=(-1)^{n-1}{\frac {m!n!}{(m+n)!}}B_{n+m}\quad {\mbox{ for }}m,n\geq 1}
∫
0
1
E
n
(
t
)
E
m
(
t
)
d
t
=
(
−
1
)
n
4
(
2
m
+
n
+
2
−
1
)
m
!
n
!
(
m
+
n
+
2
)
!
B
n
+
m
+
2
{\displaystyle \int _{0}^{1}E_{n}(t)E_{m}(t)\,dt=(-1)^{n}4(2^{m+n+2}-1){\frac {m!n!}{(m+n+2)!}}B_{n+m+2}}
Periodic Bernoulli polynomials
A periodic Bernoulli polynomial P n (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.
The following properties are of interest, valid for all
x
{\displaystyle x}
:
P
k
(
x
)
is continuous for all
k
≠
1
P
k
′
(
x
)
exists and is continuous for
k
=
0
,
k
≥
3
P
k
′
(
x
)
=
k
P
k
−
1
(
x
)
,
k
≥
3
{\displaystyle {\begin{aligned}&P_{k}(x){\text{ is continuous for all }}k\neq 1\\&P_{k}'(x){\text{ exists and is continuous for }}k=0,k\geq 3\\&P'_{k}(x)=kP_{k-1}(x),k\geq 3\end{aligned}}}
See also
References
Apostol, Tom M. (1976), Introduction to analytic number theory , Undergraduate Texts in Mathematics, New York-Heidelberg: Springer-Verlag, ISBN 978-0-387-90163-3 , MR 0434929 , Zbl 0335.10001 (See chapter 12.11)
Dilcher, K. (2010), "Bernoulli and Euler Polynomials" , in Olver, Frank W. J. ; Lozier, Daniel M.; Boisvert, Ronald F.; Clark, Charles W. (eds.), NIST Handbook of Mathematical Functions , Cambridge University Press, ISBN 978-0-521-19225-5 , MR 2723248 .
Cvijović, Djurdje; Klinowski, Jacek (1995). "New formulae for the Bernoulli and Euler polynomials at rational arguments". Proceedings of the American Mathematical Society . 123 : 1527–1535. doi :10.2307/2161144 .
Guillera, Jesus; Sondow, Jonathan (2008). "Double integrals and infinite products for some classical constants via analytic continuations of Lerch's transcendent". The Ramanujan Journal . 16 (3): 247–270. arXiv :math.NT/0506319 . doi :10.1007/s11139-007-9102-0 . (Reviews relationship to the Hurwitz zeta function and Lerch transcendent.)