On q-congruences involving harmonic numbers

We give some congruences involving $q$-harmonic numbers and alternating $q$-harmonic numbers of order $m$. Some of them are $q$-analogues of several known congruences.

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Datum:2017
Hauptverfasser: Ge, B., Ге, Б.
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Veröffentlicht: Institute of Mathematics, NAS of Ukraine 2017
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Ukrains’kyi Matematychnyi Zhurnal
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author Ge, B.
Ге, Б.
author_facet Ge, B.
Ге, Б.
author_sort Ge, B.
baseUrl_str https://umj.imath.kiev.ua/index.php/umj/oai
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datestamp_date 2019-12-05T09:26:20Z
description We give some congruences involving $q$-harmonic numbers and alternating $q$-harmonic numbers of order $m$. Some of them are $q$-analogues of several known congruences.
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fulltext UDC 512.5 B. He (College Sci., Northwest A&F Univ., Yangling, Shaanxi, China) ON \bfitq -CONGRUENCES INVOLVING HARMONIC NUMBERS* ПРО \bfitq -КОНГРУЕНЦIЇ, ЩО ВКЛЮЧАЮТЬ ГАРМОНIЧНI ЧИСЛА We give some congruences involving q-harmonic numbers and alternating q-harmonic numbers of order m. Some of them are q-analogues of several known congruences. Наведено деякi конгруенцiї, що включають q-гармонiчнi числа та знакозмiннi q-гармонiчнi числа m-го порядку. Деякi з цих конгруенцiй є q-аналогами кiлькох вiдомих конгруенцiй. 1. Introduction. For arbitrary positive integer n, the q-integer can be defined by [n]q = 1 - qn 1 - q . It is easy to see that \mathrm{l}\mathrm{i}\mathrm{m}q\rightarrow 1[n]q = n. Supposing that a \equiv b (\mathrm{m}\mathrm{o}\mathrm{d} p), we have [a]q = 1 - qa 1 - q = 1 - qb + qb(1 - qa - b) 1 - q \equiv 1 - qb 1 - q = [b]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). Here and in what follows, each congruence is considered over the polynomial ring \BbbZ [q] in the variable q with integral coefficients. For m = 1, 2, 3, . . . and n = 0, 1, 2, . . . , we define H (m) 0 = 0, H(m) n = n\sum j=1 1 jm for n \geq 1 and call it a harmonic number of order m. Those Hn = H (1) n are usually called the classical harmonic numbers. Similarly, the alternating harmonic numbers of order m are given by I (m) 0 = 0, I(m) n = n\sum j=1 ( - 1)j jm for n \geq 1. In this paper, we define Hn(q) = n\sum j=1 1 [j]q , \widetilde Hn(q) = n\sum j=1 qj [j]q , H(2) n (q) = n\sum j=1 1 [j]2q , \widetilde H(2) n (q) = n\sum j=1 qj [j]2q , H(3) n (q) = n\sum j=1 1 [j]3q , \widetilde H(3) n (q) = n\sum j=1 qj [j]3q * This work was supported by the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2017JQ1001), the Initial Foundation for Scientific Research of Northwest A&F University (No. 2452015321) and the Fundamental Research Funds for the Central Universities (No. 2452017170). c\bigcirc B. HE, 2017 ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9 1257 1258 B. HE and In(q) = n\sum j=1 ( - 1)j [j]q , I(2)n (q) = n\sum j=1 ( - 1)j [j]2q , where H0(q) = \widetilde H0(q) = H (2) 0 (q) = \widetilde H(2) 0 (q) = H (3) 0 (q) = \widetilde H(3) 0 (q) = I0(q) = I (2) 0 (q) = 0. They are q-analogues of harmonic numbers of order m. So we call them q-harmonic numbers and alternating q-harmonic numbers of order m. In view of the q-analogue of Glaishers congruence, Andrews [1] (Theorem 4) showed that Hp - 1(q) \equiv p - 1 2 (1 - q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q) and \widetilde Hp - 1(q) \equiv p - 1 2 (q - 1) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). L. L. Shi and H. Pan obtained (see [6], Theorem 1) Hp - 1(q) \equiv p - 1 2 (1 - q) + p2 - 1 24 (1 - q)2[p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q) (1.1) for each p \geq 5, which is equivalent to \widetilde Hp - 1(q) \equiv 1 - p 2 (1 - q) + p2 - 1 24 (1 - q)2[p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q). Pan established (see [5], Theorem 1.1) that for each odd prime p, there holds 2 p - 1 2\sum j=1 1 [2j]q + 2Qp(2, q) - Qp(2, q) 2[p]q \equiv \equiv \biggl( Qp(2, q)(1 - q) + p2 - 1 8 (1 - q)2 \biggr) [p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q), (1.2) where Qp(2, q) = ( - q; q)p - 1 - 1 [p]q and (x; q)n = \prod n - 1 k=0 (1 - xqk). For some material on congruences of q-harmonic numbers, see, for example, [3]. Some other q-congruences were obtained by different authors, see, for example [2, 4, 9]. Our aim of this paper is to give some congruences involving q-harmonic numbers and alternating q-harmonic numbers of order m which are q-analogues of several known identities. ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9 ON q-CONGRUENCES INVOLVING HARMONIC NUMBERS 1259 Theorem 1.1. Let p \geq 5 be a prime. Then p - 1\sum k=1 qkH (2) k (q) \equiv - p - 1 2 (1 - q) - (p - 1)(p - 3) 8 (1 - q)2[p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q), (1.3) p - 1\sum k=1 qk \widetilde H(2) k (q) \equiv p - 1 2 (1 - q) - p2 - 1 8 (1 - q)2[p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q), (1.4) p - 1\sum k=1 qkH (3) k (q) \equiv (p - 1)(p - 5) 12 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q), (1.5) p - 1\sum k=1 qk \widetilde H(3) k (q) \equiv p2 - 1 12 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). (1.6) When q \rightarrow 1, the first two q-congruences in Theorem 1.1 reduce to the following result [7] (Lemma 2.1): p - 1\sum k=1 H (2) k \equiv 0 (\mathrm{m}\mathrm{o}\mathrm{d} p2) while the last two q-congruences reduce to p - 1\sum k=1 H (3) k \equiv 0 (\mathrm{m}\mathrm{o}\mathrm{d} p). Theorem 1.2. Let p \geq 5 be a prime. Then Ip - 1(q) \equiv - 2Qp(2, q) - p - 1 2 (1 - q)+ + \biggl( Qp(2, q) 2 +Qp(2, q)(1 - q) + p2 - 1 12 (1 - q)2 \biggr) [p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q) (1.7) and I (2) p - 1(q) \equiv 1 - p 2 (1 - q)2 - 2Qp(2, q)(1 - q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). (1.8) It is clear that (1.7) and (1.8) are respectively q-analogues of Ip - 1 \equiv - 2qp(2) + qp(2) 2p (\mathrm{m}\mathrm{o}\mathrm{d} p2) and I (2) p - 1 \equiv 0 (\mathrm{m}\mathrm{o}\mathrm{d} p) (see [8], Lemma 2.1), where qp(2) = 2p - 1 - 1 p . ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9 1260 B. HE Theorem 1.3. Let p \geq 5 be a prime. Then p - 1\sum k=1 qkIk(q) \equiv \biggl( - 2Qp(2, q) - p - 1 2 (1 - q) \biggr) [p]q + + \biggl( Qp(2, q) 2 +Qp(2, q)(1 - q) + p2 - 1 12 (1 - q)2 \biggr) [p]2q (\mathrm{m}\mathrm{o}\mathrm{d} [p]3q), p - 1\sum k=1 qkI (2) k (q) \equiv 2Qp(2, q) + p - 1 2 (1 - q) - - \biggl( Qp(2, q) 2 + 3Qp(2, q)(1 - q) + (7 + p)(p - 1) 12 (1 - q)2 \biggr) [p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q). When q \rightarrow 1, the two q-congruences in Theorem 1.3 reduce respectively to the following two congruences: p - 1\sum k=1 Ik \equiv - 2qp(2)p+ qp(2) 2p2 (\mathrm{m}\mathrm{o}\mathrm{d} p3), p - 1\sum k=1 I (2) k \equiv 2qp(2) - qp(2) 2p (\mathrm{m}\mathrm{o}\mathrm{d} p2). Theorem 1.4. Let p \geq 5 be a prime. Then p - 1\sum k=1 ( - 1)k [k]q Ik(q) \equiv 2Q2 p(2, q) + (p - 1)(1 - q) + p2 - 1 12 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). The congruence in Theorem 1.4 is a q-analogue of\sum 1\leq i\leq j\leq p - 1 ( - 1)i+j ij \equiv 2q2p(2) (\mathrm{m}\mathrm{o}\mathrm{d} p). Our method of proving Theorems 1.1 – 1.4 is to write the finite sums involving (alternating) q- harmonic numbers into a linear combination of at most two (alternating) q-harmonic sums. We will provide one lemma in the next section. Section 3 is devoted to our proof of Theorems 1.1 – 1.4. 2. Auxiliary result. To prove Theorems 1.1 – 1.4, we need the following auxiliary result. Lemma 2.1. For any prime p \geq 5, there hold p - 1\sum j=1 1 [j]2q \equiv - (p - 1)(p - 5) 12 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q), (2.1) p - 1\sum j=1 qj [j]2q \equiv - p2 - 1 12 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q), (2.2) p - 1 2\sum j=1 1 [2j]2q \equiv - p2 - 1 24 (1 - q)2 - Qp(2, q)(1 - q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). (2.3) ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9 ON q-CONGRUENCES INVOLVING HARMONIC NUMBERS 1261 Proof. See [6] (Lemma 2) for the proof of (2.1) and (2.2). We now prove (2.3). It is obvious that 1 [p - 2j]q \equiv - q2j [2j]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). (2.4) Then by (2.2) and (2.4), we get - p2 - 1 12 (1 - q)2 \equiv p - 1\sum j=1 qj [j]2q = p - 1 2\sum j=1 q2j [2j]2q + p - 1 2\sum j=1 qp - 2j [p - 2j]2q \equiv \equiv 2 p - 1 2\sum j=1 q2j [2j]2q (\mathrm{m}\mathrm{o}\mathrm{d} [p]q), namely, p - 1 2\sum j=1 q2j [2j]2q \equiv - p2 - 1 24 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). (2.5) By (1.2), we have p - 1 2\sum j=1 1 [2j]q \equiv - Qp(2, q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). (2.6) Hence, with the help of q2j [2j]2q = 1 [2j]2q - (1 - q) 1 [2j]q , (2.5) and (2.6), we obtain p - 1 2\sum j=1 1 [2j]2q = p - 1 2\sum j=1 q2j [2j]2q + (1 - q) p - 1 2\sum j=1 1 [2j]q \equiv \equiv - p2 - 1 24 (1 - q)2 - Qp(2, q)(1 - q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). Lemma 2.1 is proved. 3. Proofs of Theorems 1.1 – 1.4. Proof of Theorem 1.1. We first prove (1.3) and (1.4). Observe that p - 1\sum k=1 qkH (2) k (q) = p - 1\sum j=1 1 [j]2q p - 1\sum k=j qk = p - 1\sum j=1 1 [j]2q qj - qp 1 - q = = p - 1\sum j=1 1 [j]2q \biggl( 1 - qp 1 - q - 1 - qj 1 - q \biggr) = = [p]qH (2) p - 1(q) - Hp - 1(q). ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9 1262 B. HE In view of (1.1) and (2.1), we obtain p - 1\sum k=1 qkH (2) k (q) \equiv - p - 1 2 (1 - q) - (p - 1)(p - 3) 8 (1 - q)2[p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q). This proves (1.3). By [3] (Theorem 1.2), p - 1\sum k=1 qkHk(q) \equiv 1 - p+ p - 1 2 (1 - q)[p]q + p2 - 1 24 (1 - q)2[p]2q (\mathrm{m}\mathrm{o}\mathrm{d} [p]3q) which implies that p - 1\sum k=1 qkHk(q) \equiv 1 - p+ p - 1 2 (1 - q)[p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q). (3.1) Then (1.4) follows from (1.3), (3.1) and the fact H(2) k (q) - \widetilde H(2) k (q) = (1 - q)Hk(q). We now show (1.5) and (1.6). Similarly, we can arrive at p - 1\sum k=1 qkH (3) k (q) = [p]qH (3) p - 1(q) - H (2) p - 1(q) \equiv \equiv - H (2) p - 1(q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). We use the above and (2.1) to get p - 1\sum k=1 qkH (3) k (q) \equiv (p - 1)(p - 5) 12 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q), which proves (1.5). Then (1.6) follows from (1.5) and the fact H(3) k (q) - \widetilde H(3) k (q) = (1 - q)H (2) k (q). Theorem 1.1 is proved. Proof of Theorem 1.2. We first prove (1.7). Notice that Ip - 1(q) = p - 1\sum k=1 ( - 1)k + 1 [k]q - p - 1\sum k=1 1 [k]q = = 2 p - 1 2\sum k=1 1 [2k]q - p - 1\sum k=1 1 [k]q . By (1.1) and (1.2), we obtain Ip - 1(q) \equiv - 2Qp(2, q) - p - 1 2 (1 - q)+ + \biggl( Qp(2, q) 2 +Qp(2, q)(1 - q) + p2 - 1 12 (1 - q)2 \biggr) [p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q). ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9 ON q-CONGRUENCES INVOLVING HARMONIC NUMBERS 1263 We now show (1.8). Note that I (2) p - 1(q) = p - 1\sum k=1 ( - 1)k + 1 [k]2q - p - 1\sum k=1 1 [k]2q = = 2 p - 1 2\sum k=1 1 [2k]2q - p - 1\sum k=1 1 [k]2q . With the help of (2.1) and (2.3), we get I (2) p - 1(q) \equiv 1 - p 2 (1 - q)2 - 2Qp(2, q)(1 - q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). Theorem 1.2 is proved. Proof of Theorem 1.3. Observe that p - 1\sum k=1 qkIk(q) = p - 1\sum j=1 ( - 1)j [j]q p - 1\sum k=j qk = p - 1\sum j=1 ( - 1)j [j]q qj - qp 1 - q = = p - 1\sum j=1 ( - 1)j [j]q \biggl( 1 - qp 1 - q - 1 - qj 1 - q \biggr) = [p]qIp - 1(q) and p - 1\sum k=1 qkI (2) k (q) = p - 1\sum j=1 ( - 1)j [j]2q p - 1\sum k=j qk = p - 1\sum j=1 ( - 1)j [j]2q qj - qp 1 - q = = p - 1\sum j=1 ( - 1)j [j]2q \biggl( 1 - qp 1 - q - 1 - qj 1 - q \biggr) = = [p]qI (2) p - 1(q) - Ip - 1(q). By (1.7) and (1.8), we arrive at p - 1\sum k=1 qkIk(q) \equiv \biggl( - 2Qp(2, q) - p - 1 2 (1 - q) \biggr) [p]q+ + \biggl( Qp(2, q) 2 +Qp(2, q)(1 - q) + p2 - 1 12 (1 - q)2 \biggr) [p]2q (\mathrm{m}\mathrm{o}\mathrm{d} [p]3q) and p - 1\sum k=1 qkI (2) k (q) \equiv 2Qp(2, q) + p - 1 2 (1 - q) - - \biggl( Qp(2, q) 2 + 3Qp(2, q)(1 - q) + (7 + p)(p - 1) 12 (1 - q)2 \biggr) [p]q (\mathrm{m}\mathrm{o}\mathrm{d} [p]2q), which completes the proof of Theorem 1.3. ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9 1264 B. HE Proof of Theorem 1.4. Note that p - 1\sum k=1 ( - 1)k [k]q Ik(q) = p - 1\sum j=1 ( - 1)j [j]q p - 1\sum k=j ( - 1)k [k]q = = p - 1\sum j=1 ( - 1)j [j]q \Biggl( p - 1\sum k=1 ( - 1)k [k]q - j\sum k=1 ( - 1)k [k]q + ( - 1)j [j]q \Biggr) . Hence, p - 1\sum k=1 ( - 1)k [k]q Ik(q) = 1 2 \left( I2p - 1(q) + p - 1\sum j=1 1 [j]2q \right) . (3.2) By (1.7), we have Ip - 1(q) \equiv - 2Qp(2, q) - p - 1 2 (1 - q) (\mathrm{m}\mathrm{o}\mathrm{d} [p]q), which implies that I2p - 1(q) \equiv 4Q2 p(2, q) + 2(p - 1)(1 - q) + (p - 1)2 4 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q). (3.3) With the help of (2.1), (3.2) and (3.3), we obtain p - 1\sum k=1 ( - 1)k [k]q Ik(q) \equiv 2Q2 p(2, q) + (p - 1)(1 - q) + p2 - 1 12 (1 - q)2 (\mathrm{m}\mathrm{o}\mathrm{d} [p]q), which completes the proof of Theorem 1.4. References 1. Andrews G. E. q-Analogs of the binomial coefficient congruences of Babbage, Wolstenholme and Glaisher // Discrete Math. – 1999. – 204. – P. 15 – 25. 2. Guo V. J. W., Zeng J. Some q-analogues of supercongruences of Rodriguez – Villegas // J. Number Theory. – 2014. – 145. – P. 301 – 316. 3. He B. Some congruences involving q-harmonic numbers // Ars Combin. (to appear). 4. He B., Wang K. Some congruences on q-Catalan numbers // Ramanujan J. – 2016. – 40. – P. 93 – 101. 5. Pan H. A q-analogue of Lehmers congruence // Acta Arith. – 2007. – 128. – P. 303 – 318. 6. Shi L. L., Pan H. A q-analogue of Wolstenholmes harmonic series congruence // Amer. Math. Monthly. – 2007. – 114. – P. 529 – 531. 7. Sun Z.-W. Supercongruences motivated by e // J. Number Theory. – 2015. – 147. – P. 326 – 341. 8. Sun Z.-W., Zhao L.-L. Arithmetic theory of harmonic numbers (II) // Colloq. Math. – 2013. – 130. – P. 67 – 78. 9. Tauraso R. q-analogs of some congruences involving Catalan numbers // Adv. Appl. Math. – 2012. – 48. – P. 603 – 614. Received 28.12.15, after revision — 25.03.16 ISSN 1027-3190. Укр. мат. журн., 2017, т. 69, № 9
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spelling umjimathkievua-article-17762019-12-05T09:26:20Z On q-congruences involving harmonic numbers Про \bfitq -конгруенцiї, що включають гармонiчнi числа Ge, B. Ге, Б. We give some congruences involving $q$-harmonic numbers and alternating $q$-harmonic numbers of order $m$. Some of them are $q$-analogues of several known congruences. Наведено деякi конгруенцiї, що включають $q$-гармонiчнi числа та знакозмiннi $q$-гармонiчнi числа $m$-го порядку. Деякi з цих конгруенцiй є $q$-аналогами кiлькох вiдомих конгруенцiй. Institute of Mathematics, NAS of Ukraine 2017-09-25 Article Article application/pdf https://umj.imath.kiev.ua/index.php/umj/article/view/1776 Ukrains’kyi Matematychnyi Zhurnal; Vol. 69 No. 9 (2017); 1257-1265 Український математичний журнал; Том 69 № 9 (2017); 1257-1265 1027-3190 en https://umj.imath.kiev.ua/index.php/umj/article/view/1776/758 Copyright (c) 2017 Ge B.
spellingShingle Ge, B.
Ге, Б.
On q-congruences involving harmonic numbers
title On q-congruences involving harmonic numbers
title_alt Про \bfitq -конгруенцiї, що включають гармонiчнi числа
title_full On q-congruences involving harmonic numbers
title_fullStr On q-congruences involving harmonic numbers
title_full_unstemmed On q-congruences involving harmonic numbers
title_short On q-congruences involving harmonic numbers
title_sort on q-congruences involving harmonic numbers
url https://umj.imath.kiev.ua/index.php/umj/article/view/1776
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