#### Abstract

In this paper, authors found a new and interesting identity between Changhee polynomials and some degenerate polynomials such as degenerate Bernoulli polynomials of the first and second kind, degenerate Euler polynomials, degenerate Daehee polynomials, degenerate Bell polynomials, degenerate Lah–Bell polynomials, and degenerate Frobenius–Euler polynomials and Mittag–Leffer polynomials by using -Sheffer sequences and -differential operators to find the coefficient polynomial when expressing the -th Changhee polynomials as a linear combination of those degenerate polynomials. In addition, authors derive the inversion formulas of these identities.

#### 1. Introduction

Umbral calculus from 1850 to 1970 consisted primarily of symbolic techniques for sequence manipulation, and its mathematical rigor left little room for demands. In the 1970s, Gian-Carlo Rota began building a completely rigid foundation for theories based on relatively modern ideas of linear functions, linear operators, and adjacency functions (see [1–4]). Umbral calculus contributed to the generalization of Lagrange inversion formula and has been applied in many fields such as combinatorial counting with linear recurrences and lattice path counting, graph theory using chromatic polynomials, probability theory, link invariant theory, statistics, topology, and physics (see [3]). It is being actively applied in various fields by researchers (see [1–16]).

In the past few years, many distinct umbral calculus types have begun to be studied (see [2, 4, 6, 10]). In particular, Kim–Kim defined the degenerate Sheffer sequences, -Sheffer sequence, a family of -linear functionals, and -differential operators as follows (see [2]).

Let be the field of complex numbers:and let

Let be the vector space of all linear functionals on .

Then, each real number gives rise to the linear functional on , called -linear functional given by , which is defined by (see [2])and by linear extension where , , . From (3), we havewhere is Kronecker’s symbol (see [2]).

For each real number and each positive integer , Kim and Kim defined the differential operator on in [2] as follows:and for any ,

In addition, they showed that for and ,

The order of is the smallest integer for which the coefficient of does not vanish. If , then is called invertible and such series has a multiplicative inverse of . If , then is called delta series and it has a compositional inverse of with (see [1, 2, 12, 16]).

Let be a delta series and let be an invertible series. Then, there exists a unique sequence of polynomials satisfying the orthogonality conditions (see [2])

Here, is called the -Sheffer sequence for , which is denoted by . The sequence is the -Sheffer sequence for if and only iffor all , where is the compositional inverse of such that (see [1, 2, 12, 16]).

Let and let . Then, by (8), we haveand thus we know that

The following theorem is proved by Kim and Kim [2] and is a very useful tool for researching degenerate versions of special polynomials and numbers.

Theorem 1. *Let , . Then, we havewhere*

For , the Stirling numbers of the first kind and Stirling numbers of the second kind , respectively, are given by the following (see [11, 12, 17–20]):

For each positive integer , it is well known that (see [11, 12, 17–20])

For any nonzero real number , the degenerate exponential function is defined by (see [1, 21–27])

Note that

A study of degenerate versions of some special numbers and polynomials was initiated by Carlitz who found interesting relationships connected with important numbers in combinatorics, Bernoulli polynomials, and Eulerian polynomials (see [28]). In the past decades, the study of degenerate versions of various special polynomials or numbers has been studied by many researchers (see [1, 2, 21–27, 29–32]).

By using (16), the higher-order degenerate Bernoulli polynomials are defined as follows (see [1, 10, 12, 30, 33, 34]):

When , are called the higher-order degenerate Bernoulli numbers. In addition, when , we denote .

On the other hand, Kim and Kim defined called the degenerate logarithm function as the compositional inverse function of satisfying . Then, we have (see [1, 10, 22, 24, 32])

By using (19), the degenerate Bernoulli polynomials of the second kind are defined by the generating function to be (see [16])

In the special case , are called the Bernoulli numbers of the second kind.

As degenerate version of the Stirling numbers of the first and second kind in (14), the degenerate Stirling numbers of the first kind and the degenerate Stirling numbers of the second kind are, respectively, introduced by Kim–Kim (see [1, 2, 21, 22, 24, 26–30, 35, 36]) as follows:

Let . Sinceby Theorem 1, we obtainand thus, we know thatwhere , is the falling factorial sequences. In the similar way, we also know that

The aim of this paper is to find some new and interesting identities related to the Changhee polynomials and some special polynomials by using -Sheffer sequences and -differential operators. In more detail, we find the coefficients which are also polynomials or numbers when the -th Changhee polynomial is expressed as a linear combination of some degenerate special polynomials by using the -Sheffer sequences and -differential operators (see Theorems 2–10), and by using the -Sheffer sequences and the linear combinations of those polynomials (see Theorems 5–8 and 10), and derive the inversion formulas of these identities.

#### 2. Changhee Polynomials Arising from -Sheffer Sequences

In this section, we find some relationships between the Changhee polynomials and some special polynomials arising from -Sheffer sequences.

The Changhee polynomials are given by

By (24) and (26), we obtainand, by (27), we have

By (28), we compute the first few Changhee polynomials as follows:

In addition, graphs for some Changhee polynomials are shown in Figure 1.

Note thatwhere , , .

Theorem 2. *For each nonnegative integer , we have**As the inversion formula of (31), we have*

*Proof. *Let . Sinceby Theorem 1 and (30), we haveConversely, we assume that . By (6) and (17), we obtain

Sinceand thus we know that

Theorem 3. *For each , we have**As the inversion formula of (38), we have*

*Proof. *Let . Sinceby Theorem 1, we obtainConversely, let . By (8), (12), (15) and (37), we obtainOn the other hand, by Theorem 1, we haveand hence our proofs are completed.

The degenerate Euler polynomials are defined by the generating function to be (see [28])When , are called the degenerate Euler numbers.

By (44), we know thatand so

Theorem 4. *For each , we have**As the inversion formula of (47), we have*

*Proof. *Let . Sinceby Theorem 1, we obtainConversely, we assume that . Then,On the other hand, by (11) and (46), we obtainand so our proofs are completed.

By (46), we compute the first few degenerate Euler polynomials as follows:Although , it is difficult to find , through Figure 2. But by Theorem 4, we see that , .

The degenerate Daehee polynomials are defined by the generating function to beIn the special case of , are called the degenerate Daehee numbers (see [32, 37]).

Note thatand by (24), we have

Theorem 5. *For each nonnegative integer , we have**As the inversion formula of (57), we have*

*Proof. *Let . Sinceby Theorem 1, we haveOn the other hand, by (11) and (28), we obtainConversely, we assume that . Then, by Theorem 1 and (6), we obtainOn the other hand, by (11) and (56), we obtainThe degenerate Bell polynomials are defined by the generating function to be (see [1, 23])Note thatand thusIn addition, we know that

Theorem 6. *For each nonnegative integer , we have**As the inversion formula of (69), we have*

*Proof. *Let . Sinceby Theorem 1and (67), we obtainConversely, we assume that . By (68), we obtain