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On page 206 in his lost notebook, Ramanujan recorded a seventh degree identity for his theta function $\varphi(q)$. We give an analogous ninth degree identity. We also provide an application of an entry from his second notebook on a cubic…

Number Theory · Mathematics 2025-06-03 Sun Kim , Örs Rebák

On page 206 in his lost notebook, Ramanujan recorded an incomplete septic theta function identity. Motivated by the completion of this identity by the second author, we offer cubic and quintic analogues. Using the theory generated by these…

Number Theory · Mathematics 2025-06-03 Bruce C. Berndt , Örs Rebák

On page 206 in his lost notebook, Ramanujan recorded the following enigmatic identity for his theta function $\varphi(q)$: \begin{equation*} \varphi(e^{-7\pi\sqrt{7}}) = 7^{-3/4}\varphi(e^{-\pi\sqrt{7}})\big\{1 + (\quad)^{2/7} +…

Number Theory · Mathematics 2023-04-11 Örs Rebák

Let $\Bbb Z$ and $\Bbb N$ be the set of integers and the set of positive integers, respectively. For $a_1,a_2,\ldots,a_k,n\in\Bbb N$ let $N(a_1,a_2,\ldots,a_k;n)$ be the number of representations of $n$ by…

Number Theory · Mathematics 2017-12-07 Zhi-Hong Sun

In his second notebook, Ramanujan recorded total of 23 P-Q modular equations involving theta-functions $f(-q)$, $\varphi(q)$ and $\psi(q)$. In this paper, modular equations analogous to those recorded by Ramanujan are obtained involving…

Number Theory · Mathematics 2020-08-11 M. S. Mahadeva Naika , S. Chandankumar , M. Harish

We prove a general alternate circular summation formula of theta functions, which implies a great deal of theta-function identities. In particular, we recover several identities in Ramanujan's Notebook from this identity. We also obtain two…

Combinatorics · Mathematics 2021-06-29 Jun-Ming Zhu

Let $\Bbb Z$ and $\Bbb Z^+$ be the set of integers and the set of positive integers, respectively. For $a,b,c,d,n\in\Bbb Z^+$ let $t(a,b,c,d;n)$ be the number of representations of $n$ by $ax(x+1)/2+by(y+1)/2+cz(z+1)/2+dw(w+1)/2$…

Number Theory · Mathematics 2019-10-29 Zhi-Hong Sun

In his lost notebook, Ramanujan listed 5 identities related to the false theta function $$f(q)=\sum_{n=0}^\infty (-1)^nq^{n(n+1)/2}.$$ A new combinatorial interpretation and proof of one of these identities is given. The methods of the…

Number Theory · Mathematics 2019-11-11 Hannah Burson

We define a new parameter $A'_{k,n}$ involving Ramanujan's theta-functions for any positive real numbers $k$ and $n$ which is analogous to the parameter $A_{k,n}$ defined by Nipen Saikia \cite{NS1}. We establish some modular relation…

Number Theory · Mathematics 2023-12-01 S. Chandankumar , H. S. Sumanth Bharadwaj , Vijay Yadav

Ramanujan in his second notebook recorded total of seven $P$--$Q$ modular equations involving theta--function $f(-q)$ with moduli of orders 1, 3, 5 and 15. In this paper, modular equations analogous to those recorded by Ramanujan are…

Number Theory · Mathematics 2020-05-12 S. Chandankumar , B. Hemanthkumar

Quite recently, the first author investigated vanishing coefficients of the arithmetic progressions in several $q$-series expansions. In this paper, we further study the signs of coefficients in two $q$-series expansions and establish some…

Combinatorics · Mathematics 2018-12-18 Dazhao Tang , Ernest. X. W. Xia

Let $\Bbb Z$ be the set of integers. For positive integers $a,b,c$ and $n$ let $N(a,b,c;n)$ be the number of representations of $n$ by $ax^2+by^2+cz^2$, and let $t(a,b,c;n)$ be the number of representations of $n$ by…

Number Theory · Mathematics 2018-12-12 Zhi-Hong Sun

On pages 338 and 339 in his first notebook, Ramanujan defined the remarkable product of theta-functions $a_{m, n}$. Also he recorded eighteen explicit values depending on two parameters, namely, $m$, and $n$, where these are odd integers.…

Number Theory · Mathematics 2020-05-01 D. J. Prabhakaran , K. Ranjith kumar

In this paper, we study the $5$-dissections of certain Ramanujan's theta functions, particularly $\psi(q)\psi(q^2), \varphi(-q)$ and $\varphi(-q)\varphi(-q^2)$, and derive an identity for $q(q;q)_{\infty}^6/(q^5;q^5)_{\infty}^6$ in terms of…

Number Theory · Mathematics 2024-10-21 Russelle Guadalupe

In this work, we investigate internal congruences modulo arbitrary powers of $3$ for two functions arising from Ramanujan's classical theta functions $\varphi(q)$ and $\psi(q)$. By letting \begin{align*} \sum_{n\ge 0} ph_3(n)…

Number Theory · Mathematics 2023-09-14 Shane Chern , Dazhao Tang

In this article, we define functions analogous to Ramanujan's function $f(n)$ defined in his famous paper "Modular equations and approximations to $\pi$". We then use these new functions to study Ramanujan's series for $1/\pi$ associated…

Number Theory · Mathematics 2018-09-12 Alex Berkovich , Heng Huat Chan , Michael J. Schlosser

On page 3 of his lost notebook, Ramanujan defines the Appell-Lerch sum $$\phi(q):=\sum_{n=0}^\infty \dfrac{(-q;q)_{2n}q^{n+1}}{(q;q^2)_{n+1}^2},$$ which is connected to some of his sixth order mock theta functions. Let $\sum_{n=1}^\infty…

Number Theory · Mathematics 2023-01-30 Nayandeep Deka Baruah , Nilufar Mana Begum

In this paper we obtain some new transformation formula for Ramanujan summation formula and also establish some eta-function identities. we also deduce a q-Gamma function identity, n q-integral and some interesting series representation.

Number Theory · Mathematics 2007-05-23 C. Adiga , N. Anitha , T. Kim

We have found several summation formulas that extend Ramanujan's psi sum. First contains a parameter $\alpha=1/N$, $N$ is a positive integer, and transforms to $q$-beta integral in the limit $N\to\infty$. The other is a $q$-analogue of…

Classical Analysis and ODEs · Mathematics 2012-05-01 N. M. Vildanov

We study Ramanujan's cubic continued fraction and explicit evaluations of theta-functions

Number Theory · Mathematics 2007-05-23 C. Adiga , T. Kim , M. S. Mahadeva Naika , H. S. Madhusudhan
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