A RESEARCH on the GENERALIZED POLY-BERNOULLI POLYNOMIALS with VARIABLE A†
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J. Appl. Math. & Informatics Vol. 36(2018), No. 5 - 6, pp. 475 - 489 https://doi.org/10.14317/jami.2018.475 A RESEARCH ON THE GENERALIZED POLY-BERNOULLI POLYNOMIALS WITH VARIABLE ay N.S. JUNG AND C.S. RYOO∗ Abstract. In this paper, by using the polylogarithm function, we intro- duce a generalized poly-Bernoulli numbers and polynomials with variable a. We find several combinatorial identities and properties of the polynomi- als. We give some properties that is connected with the Stirling numbers of second kind. Symmetric properties can be proved by new configured special functions. We display the zeros of the generalized poly-Bernoulli polynomials with variable a and investigate their structure. AMS Mathematics Subject Classification : 11B68, 11B73, 11B75. Key words and phrases : Generalized poly-Bernoulli polynomials with variable a, Stirling numbers of the second kind, polylogarithm function, power sum polynomials, special function. 1. Introduction Recently, one of the researchers' interests in many fields is the applications of Bernoulli numbers and polynomials. Many researchers have studied Bernoulli numbers and polynomials and focus on expansion and generalization of theirs. Specially, it is being studied actively about poly-Bernoulli numbers and polyno- mials is concerned with polylogarithm function(cf. [1-9]). In this paper, we use the following notations. N = f1; 2; 3;::: g denotes the set of natural numbers, Z+ denotes the set of nonnegative integers, Z denotes the set of integers, and C denotes the set of complex numbers, respectively. The classical Bernoulli polynomials Bn(x) are given by the generating function 1 t X tn ext = B (x) ; (cf. [1, 2, 3, 4, 5]): (1:1) et − 1 n n! n=0 (k) (k) When x = 0;Bn;q = Bn;q(0) are called poly-Bernoulli numbers. Received January 9, 2018. Revised July 25, 2018. Accepted August 5, 2018. ∗Corresponding author. yThis work was supported by 2018 Hannam University Research Fund. ⃝c 2018 Korean SIGCAM and KSCAM. 475 476 N.S. Jung, C.S. Ryoo Definition 1.1. For a 2 C n f0g, we define a generalized Bernoulli polynomials Bn(x; a) with variable a by the following generating function 1 t X tn 2π ext = B (x; a) ; jtj < : (1:2) eat − 1 n n! jaj n=0 When a = 1, it is equal to the classical Bernoulli polynomials. The polyloga- rithm function Lik(x) is defined by 1 X xn Li (x) = ; (k 2 Z); (cf. [1, 2, 3, 5, 7, 8, 9, 12]): (1:3) k nk n=1 For some k, the polylogarithm functions Lik(x) are as follows: x Li (x) = −log(1 − x); Li (x) = ; 1 0 1 − x x x2 + x Li−1(x) = ; Li−2(x) = ;:::: (1 − x)2 (1 − x)3 For n 2 Z+; k 2 Z, the poly-Bernoulli polynomials is defined by 1 Li (1 − e−t) X tn k ext = B(k)(x) ; (1:4) et − 1 n n! n=0 where 1 X xn Li (x) = k nk n=1 is k-th polylogarithm function(cf. [1, 2, 3, 4, 5, 7, 12]). When k = 1, Li1(x) = −t −log(1−x) and Li1(1−e ) = t. Using the result of polylogarithm function, we deduce that the poly Bernoulli polynomials is identical to the Bernoulli polyno- mials when k = 1. The classical Stirling numbers of the second kind S2(n; m) are defined by the relations Xn n x = S2(n; m)(x)m; m=0 where (x)n = x(x − 1)(x − 2) ··· (x − n + 1) is falling factorial. The Stirling numbers of the second kind is defined by 1 X tn (et − 1)m S (n; m) = ; (cf. [4, 6, 9, 10, 11]): (1:5) 2 n! m! n=m In this paper, we introduce a generalized poly-Bernoulli numbers and polynomi- als with variable a. The properties of the Bernoulli polynomials with parameters were studied in [5, 8]. We construct a generalized poly-Bernoulli polynomials with variable a and give some relations between the generalized poly-Bernoulli polynomials and the classical Bernoulli polynomials. We also investigate sev- eral identities that are connected with the Stirling numbers of the second kind. A research on the generalized poly-Bernoulli polynomials with variable a 477 Furthermore, we find some symmetric identities by using special functions and power sum polynomials. 2. Generalized poly-Bernoulli polynomials with variable a (k) In this section, we introduce a generalized poly-Bernoulli numbers Bn (a) (k) and polynomials Bn (x; a) with variable a by the generating functions. We give some identities of the polynomials, and find a relation that is connected with classical Bernoulli polynomials. Definition 2.1. For n 2 Z+ and k 2 Z, the generalized poly-Bernoulli polyno- (k) mials Bn (x; a) with variable a are defined by means of the following generating function 1 Li (1 − e−t) X tn k ext = B(k)(x; a) (2:1) eat − 1 n n! n=0 where 1 X tn Li (t) = k nk n=1 (k) (k) is the k-th polylogarithm function. When x = 0, Bn (a) = Bn (0; a) are called the generalized poly-Bernoulli numbers with variable a. When the condition al- low a = 1, it is trivial that the generalized poly-Bernoulli polynomials is reduced to poly-Bernoulli polynomials. From (2.1), we have a relation between the generalized poly-Bernoulli numbers and polynomials. Theorem 2.2. Let n; m be a nonnegative integers and k 2 Z. We have ( ) Xn n B(k)(mx; a) = (m − 1)n−1B(k)(x; a)xn−l: (2:2) n l l l=0 Proof. For n; m 2 Z+, k 2 Z; we get ! 1 1 ( ) X tn X Xn n tn B(k)(mx; a) = B(k)(x; a)(m − 1)n−1xn−l : n n! l l n! n=0 n=0 l=0 Therefore, we obtain above result. Corollary 2.3. Let m > 0, n ≥ 0, k 2 Z. We get ( ) Xn n B(k)(mx; a) = mn−lB(k)(a)xn−l: n l l l=0 When m = 1, it is satisfies ( ) Xn n B(k)(x; a) = B(k)(a)xn−l: n l l l=0 478 N.S. Jung, C.S. Ryoo If x is replaced x + y in Corollary 2.3, we get the next addition theorem. Theorem 2.4. For n 2 Z+ and k 2 Z, we have ( ) Xn n B(k)(x + y; a) = B(k)(x; a)yn−l: n l l l=0 Proof. Let n 2 Z+, k 2 Z. Then we get 1 X tn Li (1 − e−t) B(k)(x + y; a) = k e(x+y)t n n! eat − 1 n=0 ! 1 ( ) X Xn n tn = B(k)(x; a)yn−l : l l n! n=0 l=0 Thus, we get the explicit result. Theorem 2.5. For n 2 Z+ and k 2 Z, we derive − ( ) nX1 n B(k)(x + 1; a) − B(k)(x; a) = B(k)(x; a): n n l l l=0 Proof. Let n 2 Z+; k 2 Z. From (2.1), we have 1 1 X tn X tn B(k)(x + 1; a) − B(k)(x; a) n n! n n! n=0 n=0 Li (1 − e−t) = k ext(et − 1) eat − 1 1 − ( ) X nX1 n tn = B(k)(x; a) : l l n! n=0 l=0 Comparing the coefficient on both sides, we obtain the desired result. By using the binomials series and the definition of polylogarithm function, we derive the result as below. Theorem 2.6. For n 2 Z+ and k 2 Z, we have 1 ( ) X Xl mX+1 m + 1 (−1)r+1(x − r + al − am)n B(k)(x; a) = : n r (m + 1)n l=0 m=0 r=0 A research on the generalized poly-Bernoulli polynomials with variable a 479 Proof. Let n 2 Z+; k 2 Z: From (1.3), we obtain ! ! 1 1 Li (1 − e−t) X X (1 − e−t)l+1 k ext = (−1) emat ext eat − 1 (l + 1)k m=0 l=0 1 X Xl (1 − e−t)m+1 = (−1) e(l−m)at ext (m + 1)k l=0 m=0 ! ! 1 ( ) X Xl e(l−m)at mX+1 m + 1 = (−1) (−1)re(x−r)t (m + 1)k r l=0 m=0 r=0 1 1 ( ) X X Xl mX+1 m + 1 (−1)r+1(x − r + al − am)n tn = r (m + 1)k n! n=0 l=0 m=0 r=0 Therefore, we get 1 ( ) X Xl mX+1 m + 1 (−1)r+1(x − r + al − am)n B(k)(x; a) = : n r (m + 1)k l=0 m=0 r=0 Similarly, we find next result that is related with the generalized Bernoulli polynomials with variable a. Theorem 2.7. Let n 2 Z+ and k 2 Z: Then we have 1 ( ) X 1 Xl+1 l + 1 B (x − r; a) B(k)(x; a) = (−1)r n+1 : n (l + 1)k r n + 1 l=0 r=0 Proof. For n 2 Z+ and k 2 Z, we have 1 Li (1 − e−t) X (1 − e−t)l ext k ext = eat − 1 lk eat − 1 l=1 1 ( ) X 1 Xl+1 l + 1 e(x−r)t = (−1)r (l + 1)k r eat − 1 n=0 r=0 ! 1 1 ( ) X X 1 Xl+1 l + 1 B (x − r; a) tn = (−1)r n+1 : (l + 1)k r n + 1 n! n=0 l=0 r=0 So, we easily get 1 ( ) X 1 Xl+1 l + 1 B (x − r; a) B(k)(x; a) = (−1)r n+1 : n (l + 1)k r n + 1 l=0 r=0 480 N.S.