1 Introduction

As is well known, the Bernoulli polynomials of the second kind are defined by the generating function to be

t log ( 1 + t ) ( 1 + t ) x = n = 0 b n (x) t n n ! (see [1–3]).
(1)

When x=0, b n = b n (0) are called the Bernoulli numbers of the second kind. The first few Bernoulli numbers b n of the second kind are b 0 =1, b 1 =1/2, b 2 =1/12, b 3 =1/24, b 4 =19/720, b 5 =3/160, .

From (1), we have

b n (x)= l = 0 n ( n l ) b l ( x ) n l ,
(2)

where ( x ) n =x(x1)(xn+1) (n0). The Stirling number of the second kind is defined by

x n = l = 0 n S 2 (n,l) ( x ) l (n0).
(3)

The ordinary Bernoulli polynomials are given by

t e t 1 e x t = n = 0 B n (x) t n n ! (see [1–18]).
(4)

When x=0, B n = B n (0) are called Bernoulli numbers.

It is well known that the classical poly-logarithmic function Li k (x) is given by

Li k (x)= n = 1 x n n k (kZ)(see [8–10]).
(5)

For k=1, Li 1 (x)= n = 1 x n n =log(1x). The Stirling number of the first kind is defined by

( x ) n = l = 0 n S 1 (n,l) x l (n0)(see [16]).
(6)

In this paper, we consider the poly-Bernoulli numbers and polynomials of the second kind and presents new and explicit formulas for calculating the poly-Bernoulli number and polynomial and the Stirling number of the second kind.

2 Poly-Bernoulli numbers and polynomials of the second kind

For kZ, we consider the poly-Bernoulli polynomials b n ( k ) (x) of the second kind:

Li k ( 1 e t ) log ( 1 + t ) ( 1 + t ) x = n = 0 b n ( k ) (x) t n n ! .
(7)

When x=0, b n ( k ) = b n ( k ) (0) are called the poly-Bernoulli numbers of the second kind.

Indeed, for k=1, we have

Li k ( 1 e t ) log ( 1 + t ) ( 1 + t ) x = t log ( 1 + t ) ( 1 + t ) x = n = 0 b n (x) t n n ! .
(8)

By (7) and (8), we get

b n ( 1 ) (x)= b n (x)(n0).
(9)

It is well known that

t ( 1 + t ) x 1 log ( 1 + t ) = n = 0 B n ( n ) (x) t n n ! ,
(10)

where B n ( α ) (x) are the Bernoulli polynomials of order α which are given by the generating function to be

( t e t 1 ) α e x t = n = 0 B n ( α ) (x) t n n ! (see [1–18]).

By (1) and (10), we get

b n (x)= B n ( n ) (x+1)(n0).

Now, we observe that

(11)

Thus, by (11), we get

n = 0 b n ( 2 ) ( x ) t n n ! = ( 1 + t ) x log ( 1 + t ) 0 t x e x 1 d x = ( 1 + t ) x log ( 1 + t ) l = 0 B l l ! 0 t x l d x = ( t log ( 1 + t ) ) ( 1 + t ) x l = 0 B l ( l + 1 ) t l l ! = n = 0 { l = 0 n ( n l ) B l b n l ( x ) l + 1 } t n n ! .
(12)

Therefore, by (12), we obtain the following theorem.

Theorem 2.1 For n0 we have

b n ( 2 ) (x)= l = 0 n ( n l ) B l b n l ( x ) l + 1 .

From (11), we have

n = 0 b n ( k ) ( x ) t n n ! = Li k ( 1 e t ) log ( 1 + t ) ( 1 + t ) x = t log ( 1 + t ) Li k ( 1 e t ) t ( 1 + t ) x .
(13)

We observe that

1 t Li k ( 1 e t ) = 1 t n = 1 1 n k ( 1 e t ) n = 1 t n = 1 ( 1 ) n n k n ! l = n S 2 ( l , n ) ( t ) l l ! = 1 t l = 1 n = 1 l ( 1 ) n + l n k n ! S 2 ( l , n ) t l l ! = l = 0 n = 1 l + 1 ( 1 ) n + l + 1 n k n ! S 2 ( l + 1 , n ) l + 1 t l l ! .
(14)

Thus, by (10) and (14), we get

n = 0 b n ( k ) ( x ) t n n ! = ( m = 0 b m ( x ) t m m ! ) { l = 0 ( p = 1 l + 1 ( 1 ) p + l + 1 p k p ! S 2 ( l + 1 , p ) l + 1 ) t l l ! } = n = 0 { l = 0 n ( n l ) ( p = 1 l + 1 ( 1 ) p + l + 1 p ! p k S 2 ( l + 1 , p ) l + 1 ) b n l ( x ) } t n n ! .
(15)

Therefore, by (15), we obtain the following theorem.

Theorem 2.2 For n0, we have

b n ( k ) (x)= l = 0 n ( n l ) ( p = 1 l + 1 ( 1 ) p + l + 1 p k p ! S 2 ( l + 1 , p ) l + 1 ) b n l (x).

By (7), we get

n = 0 ( b n ( k ) ( x + 1 ) b n ( k ) ( x ) ) t n n ! = Li k ( 1 e t ) log ( 1 + t ) ( 1 + t ) x + 1 Li k ( 1 e t ) log ( 1 + t ) ( 1 + t ) x = t Li k ( 1 e t ) log ( 1 + t ) ( 1 + t ) x = ( t log ( 1 + t ) ( 1 + t ) x ) Li k ( 1 e t ) = ( l = 0 b l ( x ) l ! t l ) { p = 1 ( m = 1 p ( 1 ) m + p m ! m k S 2 ( p , m ) ) } t p p !
(16)
= n = 1 ( p = 1 n m = 1 p ( 1 ) m + p m k m ! S 2 ( p , m ) b n p ( x ) n ! ( n p ) ! p ! ) t n n ! = n = 1 { p = 1 n m = 1 p ( n p ) ( 1 ) m + p m ! m k S 2 ( p , m ) b n p ( x ) } t n n ! .
(17)

Therefore, by (16), we obtain the following theorem.

Theorem 2.3 For n1, we have

b n ( k ) (x+1) b n ( k ) (x)= p = 1 n m = 1 p ( n p ) ( 1 ) m + p m ! m k S 2 (p,m) b n p (x).
(18)

From (13), we have

n = 0 b n ( k ) ( x + y ) t n n ! = ( Li k ( 1 e t ) log ( 1 + t ) ) k ( 1 + t ) x + y = ( Li k ( 1 e t ) log ( 1 + t ) ) k ( 1 + t ) x ( 1 + t ) y = ( l = 0 b l ( k ) ( x ) t l l ! ) ( m = 0 ( y ) m t m m ! ) = n = 0 ( l = 0 n ( y ) l b n l ( k ) ( x ) n ! ( n l ) ! l ! ) t n n ! = n = 0 ( l = 0 n ( n l ) b n l ( k ) ( x ) ( y ) l ) t n n ! .
(19)

Therefore, by (17), we obtain the following theorem.

Theorem 2.4 For n0, we have

b n ( k ) (x+y)= l = 0 n ( n l ) b n l ( k ) (x) ( y ) l .