In this paper, the author defines the function , the number of singular overpartition pairs of n without multiples of k in which no part is divisible by δ and only parts congruent to ± i, ± j modulo δ may be overlined.
Andrews introduced to combinatorial objects, which he called singular overpartitions and proved that these singular overpartitions depend on two parameters δ and i can be enumerated by the function , which gives the number of overpartitions of n in which no part divisible by δ and parts ≡ ± i(Mod δ) may be overlined.
Using classical spirit of q-series techniques, the author obtains congruences modulo 4 for , and .
The results established in this work are extension to those proved in Andrews’ singular overpatition pairs of n.
1. Introduction
For |ab| < 1, Ramanujan's general theta function f(a, b) is defined as
where the product representations arise from Jacobi's triple product identity [1, p. 35, Entry 19].
Throughout the paper, we use the standard q-series notation, and fk is defined as
The special cases of f(a, b) are
and
A partition of a positive integer n is a nonincreasing sequence of positive integers whose sum is n. An overpartition, introduced by Corteel and Lovejoy [2], of a nonnegative integer n is a nonincreasing sequence of natural numbers whose sum is n in which the first occurrence of a number may be overlined.
Recently, G. E. Andrews [3] defined combinatorial objects, which he called singular overpartitions and proved that these singular overpartitions depend on two parameters δ and i can be enumerated by the function , which gives the number of overpartitions of n in which no part divisible by δ and parts ≡ ±i (mod δ) may be overlined. The generating function of is
He also proved that
Andrews [3] proves that, for all n ≥ 0, , where is the number of overpartitions of n into parts not divisible by 3. The function , which counts the number of overpartitions of n into parts not divisible by ℓ, plays a key role in the work of Lovejoy [4].
Chen et al. [5] have generalized (1.7) and proved some congruences modulo 2, 3, 4 and 8 for . They also proved some congruence for , and modulo powers of 2 and 3. More recently, Ahmed and Baruah [6] have found some new congruences for , , , and modulo 18, 36. Chen [7] has also found some congruences modulo powers of 2 for , . Yao [8] has proved congruences modulo 16, 32, 64 for . Naika and Gireesh [9] have found some congruences modulo 6, 12, 16, 18, 24, 48 and 72 for . Naika and Nayaka [10] have proved some congruences for modulo powers of 2 and 3. They have also proved in a paper [11] modulo 4 for and .
In [12, 13], Naika et al. have defined the Andrews' singular overpartition pairs of n. Let denote the number of Andrews' singular overpartition pairs of n in which no part is divisible by δ and only parts congruent to ± i, ± j modulo δ may be overlined. Andrews' singular overpartition pair π of n is a pair of Andrews' singular overpartitions (λ, μ) such that the sum of all of the parts is n. They also established Ramanujan-like congruences for modulo 3,9, 27 and infinite families of congruences for modulo 4, 6 and 9.
In this paper, we define the function , the number of singular overpartition pairs of n without multiples of k in which no part is divisible by δ and only parts congruent to ± i, ± j modulo δ may be overlined. The generating function of is given by
In this paper, we establish some congruences modulo 4 for , and . The main results of this paper can be stated as follows.
For all integers α ≥ 0 and n ≥ 0,
Let p be a prime ≥ 5, . Then for all integers α ≥ 1, and n ≥ 0,
Let p be a prime ≥ 5, . Then for all integers α ≥ 0, and n ≥ 0,
For all integers α ≥ 0 and n ≥ 0,
For any prime p ≥ 5, α ≥ 0 and n ≥ 0, we have
For any prime p ≥ 5, α ≥ 0, n ≥ 0 and l = 1, 2, …p − 1, we have
For all integers α ≥ 0 and n ≥ 0,
For any prime p ≥ 5, α ≥ 0 and n ≥ 0, we have
For any prime p ≥ 5, α ≥ 0, n ≥ 0 and l = 1, 2, …p − 1, we have
2. Preliminary results
We need the following few dissection formulas to prove our main results,
The following two dissections hold:
The following two dissections hold:
Eqn (2.3) was proved by Baruah and Ojah [16]. Replacing q by − q in (2.3) and using the fact that , we get (2.4).
The following two dissections hold:
Xia and Yao [17] gave a proof of Lemma (2.3). Replacing q by − q in (2.5) and using the fact that , we get (2.6).
The following two dissections hold:
The following two dissections hold:
The following three dissections hold:
One can see this identity in [20].
For any prime p and positive integer n,
3. Proof of Theorem (1.1)
Setting i = 2, j = 4, δ = 8 and k = 3 in (1.8), we see that
By the definition of f(a, b) and the well-known Jacobi triple product identity, we get
Equating odd parts of the aforementioned equation, we obtain
Extracting the terms involving q2n from both sides of (3.6), we have
Using (2.11) in the aforementioned equation, we obtain
which implies
Congruence (1.9) easily follows from the aforementioned equation.
From (3.6), we have
Extracting the terms involving q2n+1 from (3.15), dividing by q and replacing q2 by q, we arrive at
Extracting the terms involving q2n from both sides of (3.18), we have
From (3.18), we have
From (3.15), we get
Extracting the terms involving q2n from both sides of (3.24), we find that
which implies
Extracting the terms involving q2n+1 from (3.26), dividing by q and replacing q2 by q, we arrive at
Extracting the terms involving q2n from both sides of (3.24), we have
which implies
which implies
Extracting the terms involving q2n from (3.37) and replacing q2 by q, we obtain
From (3.37), we have
From (3.34), we arrive at
Extracting the terms involving q2n+1 from (3.9), dividing by q and replacing q2 by q, we obtain
From equations (3.45), (3.30) and (3.40), we obtain (1.18).
4. Proof of Theorem (1.2)
Extracting the terms involving q2n from (3.45) and replacing q2 by q, we have
define
For a prime, p ≥ 5 or , consider
therefore,
Since the congruence relation (4.4) holds if and only if both . Therefore, if we substitute Lemma (2.7) into (4.2) and then extract the terms in which the powers of q are congruent to modulo p and then divide by , we find that
which implies that
and for n ≥ 0,
where i is an integer and 1 ≤ i ≤ p − 1. By induction, we see that for n ≥ 0 and α ≥ 0,
5. Proof of Theorem (1.3)
6. Proof of Theorem (1.4)
Setting i = 2, j = 4, δ = 8 and k = 5 in (1.8), we see that
By the definition of f(a, b) and the well-known Jacobi triple product identity, we get
Equating odd parts of the aforementioned equation, we obtain
7. Proof of Theorem (1.5)
From (6.5), we have
Employing Lemma (2.7) into (7.1), it can be see that
which implies
Therefore,
Using the aforementioned relation and by induction on α, we arrive at (1.23).
8. Proof of Theorem (1.6)
Combining (7.2) with Theorem (1.5), we derive that for α ≥ 0,
Therefore, it follows that
where l = 1, 2, …, p − 1, we obtain (1.24).
9. Proof of Theorem (1.7)
Setting i = 2, j = 4, δ = 12 and k = 3 in (1.8), we see that
By the definition of f(a, b) and the well-known Jacobi triple product identity, we get
Equating odd parts of the aforementioned equation, we obtain
Ramanujan recorded the following identity in his third note book:
Congruence (1.25) easily follows from the aforementioned equation.
Extracting the terms involving q3n+1 from (9.7), dividing by q and replacing q3 by q, we arrive at
From (9.9), we can reduce that
Extracting the terms involving q3n+1 from (9.11), dividing by q and replacing q3 by q, we have
From (9.12), we find that
Using the aforementioned relation and by induction on α, we have
10. Proof of Theorem (1.8)
From (9.11), we find that
Employing Lemma (2.7) into (10.2), it can be see that
which implies
Therefore,
Using the aforementioned relation and by induction on α, we arrive at (1.31).
11. Proof of Theorem (1.9)
Combining (10.3) with Theorem (1.8), we derive that for α ≥ 0,
Therefore, it follows that
where l = 1, 2, …, p − 1, we obtain (1.32).
Dedicated to Prof. M. S. Mahadeva Naika on his 62nd birthday.
Acknowledgement:
The authors would like to thank the anonymous referee for his valuable suggestions to improve the quality of our paper.
Funding: This research received no specific grants from any funding agency in the public, commercial or not for profit sectors.
